FreeBSD's libexecinfo defines backtrace with a size_t for the size
argument and return type. This almost certainly doesn't make sense, but
what's done is done so cast the output to allow compilation. Otherwise
we get:

.../flang/runtime/stop.cpp:165:13: error: non-constant-expression cannot
be narrowed from type 'size_t' (aka 'unsigned long') to 'int' in
initializer list [-Wc++11-narrowing]
  165 |   int nptrs{backtrace(buffer, MAX_CALL_STACK)};
      |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Fixed build failures in old PRs due to missing files

Reverts llvm/llvm-project#117603 due to failed buildbot
https://lab.llvm.org/buildbot/#/builders/152/builds/710

The important bit of the log was
```
FAILED: CMakeFiles/FortranRuntime.dir/stop.cpp.o 
ccache /usr/bin/g++ -DFLANG_LITTLE_ENDIAN=1 -DGTEST_HAS_RTTI=0 -DRT_USE_LIBCUDACXX=1 -D_DEBUG -D_GLIBCXX_ASSERTIONS -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/home/buildbot/worker/as-builder-7/ramdisk/flang-runtime-cuda-gcc/llvm-project/flang/runtime/../include -I/home/buildbot/worker/as-builder-7/ramdisk/flang-runtime-cuda-gcc/build -I/home/buildbot/worker/third-party/nv/cccl/libcudacxx/include -fvisibility-inlines-hidden -Werror=date-time -fno-lifetime-dse -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wno-missing-field-initializers -Wimplicit-fallthrough -Wno-nonnull -Wno-class-memaccess -Wno-redundant-move -Wno-pessimizing-move -Wno-noexcept-type -Wdelete-non-virtual-dtor -Wsuggest-override -Wno-comment -Wno-misleading-indentation -Wctad-maybe-unsupported -fdiagnostics-color -ffunction-sections -fdata-sections -fno-lto -O3 -DNDEBUG   -U_GLIBCXX_ASSERTIONS -U_LIBCPP_ENABLE_ASSERTIONS -UNDEBUG -std=c++17  -fno-exceptions -fno-unwind-tables -fno-asynchronous-unwind-tables -fno-rtti -MD -MT CMakeFiles/FortranRuntime.dir/stop.cpp.o -MF CMakeFiles/FortranRuntime.dir/stop.cpp.o.d -o CMakeFiles/FortranRuntime.dir/stop.cpp.o -c /home/buildbot/worker/as-builder-7/ramdisk/flang-runtime-cuda-gcc/llvm-project/flang/runtime/stop.cpp
/home/buildbot/worker/as-builder-7/ramdisk/flang-runtime-cuda-gcc/llvm-project/flang/runtime/stop.cpp:19:10: fatal error: llvm/Config/config.h: No such file or directory
   19 | #include "llvm/Config/config.h"
      |          ^~~~~~~~~~~~~~~~~~~~~~
compilation terminated.
```

CC @dty2

Hey guys, I found that Flang's built-in ABORT function is incomplete
when I was using it. Compared with gfortran's ABORT (which can both
abort and print out a backtrace), flang's ABORT implementation lacks the
function of printing out a backtrace. This feature is essential for
debugging and understanding the call stack at the failure point.

To solve this problem, I completed the "// TODO:" of the abort function,
and then implemented an additional built-in function BACKTRACE for
flang. After a brief reading of the relevant source code, I used
backtrace and backtrace_symbols in "execinfo.h" to quickly implement
this. But since I used the above two functions directly, my
implementation is slightly different from gfortran's implementation (in
the output, the function call stack before main is additionally output,
and the function line number is missing). In addition, since I used the
above two functions, I did not need to add -g to embed debug information
into the ELF file, but needed -rdynamic to ensure that the symbols are
added to the dynamic symbol table (so that the function name will be
printed out).

Here is a comparison of the output between gfortran 's backtrace and my
implementation:
gfortran's implemention output:
```
#0  0x557eb71f4184 in testfun2_
        at /home/hunter/plct/fortran/test.f90:5
#1  0x557eb71f4165 in testfun1_
        at /home/hunter/plct/fortran/test.f90:13
#2  0x557eb71f4192 in test_backtrace
        at /home/hunter/plct/fortran/test.f90:17
#3  0x557eb71f41ce in main
        at /home/hunter/plct/fortran/test.f90:18
```
my impelmention output:
```
Backtrace:
#0 ./test(_FortranABacktrace+0x32) [0x574f07efcf92]
#1 ./test(testfun2_+0x14) [0x574f07efc7b4]
#2 ./test(testfun1_+0xd) [0x574f07efc7cd]
#3 ./test(_QQmain+0x9) [0x574f07efc7e9]
#4 ./test(main+0x12) [0x574f07efc802]
#5 /usr/lib/libc.so.6(+0x25e08) [0x76954694fe08]
#6 /usr/lib/libc.so.6(__libc_start_main+0x8c) [0x76954694fecc]
#7 ./test(_start+0x25) [0x574f07efc6c5]
```
test program is:
```
function testfun2() result(err)
  implicit none
  integer :: err
  err = 1
  call backtrace
end function testfun2

subroutine testfun1()
  implicit none
  integer :: err
  integer :: testfun2

  err = testfun2()
end subroutine testfun1

program test_backtrace
  call testfun1()
end program test_backtrace
```
I am well aware of the importance of line numbers, so I am now working
on implementing line numbers (by parsing DWARF information) and
supporting cross-platform (Windows) support.

According to the C99 standard, <fenv.h> may not define FE_INVALID and
the likes. Even if C++11 mandate them, musl and emscripten don't provide
them, so handle that case.

The semantic checks and runtime have been supported. This supports the
lowering of intrinsic ABORT.

`gfortran` prints a backtrace before abort, unless `-fno-backtrace` is
given. This is good to use. The intrinsic BACKTRACE is not supported
yet, so add TODO in the runtime.

This extention is needed in SPEC2017 521.wrf_r in
https://github.com/llvm/llvm-project/issues/55955.

Reviewed By: klausler

Differential Revision: https://reviews.llvm.org/D130439

As per Steve Scalpone's suggestion, I've renamed the runtime routine to
better evoke its purpose.

I implemented a routine called "Crash" and added a test.

Differential Revision: https://reviews.llvm.org/D118703

The title says it all.

I implemented a routine called "Crash" and added a test.

Differential Revision: https://reviews.llvm.org/D118509

In 'STOP bye bye', do not print 'Fortran STOP:` before 'bye bye' when
NO_STOP_MESSAGE environment variable is set at runtime.

Also only exit with code 1 in StopStatementText if this is an ERROR STOP.
This matches other compiler behaviors.

Move STOP related unit tests in their own test file and add new tests to
cover this change.

Differential Revision: https://reviews.llvm.org/D114152

When an environment variable NO_STOP_MESSAGE=1 is set,
assume that STOP statements with a successful code
have QUIET=.TRUE.

Differential Revision: https://reviews.llvm.org/D113701