[llvm] [flang-rt][build] Disable build-time warning of '-Wshift-count-negative' from g++ compiler and remove unsupported floating-point data. (PR #174915)

[liao jun via llvm-commits]

zjlcd wrote:

This is my test script for Fortran test from llvm-test-suite(all PR in one):
```
#!/usr/bin/bash
work_dir=`pwd`
llvm_build_dir=$work_dir/llvm-project/build
llvm_install_dir=$work_dir/install

export PATH=$llvm_install_dir/bin:$PATH
export LD_LIBRARY_PATH=$llvm_install_dir/lib:$LD_LIBRARY_PATH

cd $work_dir
git clone https://github.com/llvm/llvm-test-suite.git
cd llvm-test-suite
rm -rf test-suite-build
mkdir test-suite-build
cd test-suite-build

cmake -G "Unix Makefiles" \
      -DCMAKE_BUILD_TYPE="Release" \
      -DCMAKE_C_COMPILER=$llvm_install_dir/bin/clang \
      -DCMAKE_CXX_COMPILER=$llvm_install_dir/bin/clang++ \
      -DCMAKE_Fortran_COMPILER=$llvm_install_dir/bin/flang \
      -DTEST_SUITE_COLLECT_CODE_SIZE:STRING=OFF \
      -DTEST_SUITE_SUBDIRS:STRING="Fortran" \
      -DTEST_SUITE_FORTRAN:STRING=ON \
      -DTEST_SUITE_FORTRAN_ISO_C_HEADER_DIR=$llvm_install_dir/include/flang \
      -DTEST_SUITE_LIT=$llvm_build_dir/bin/llvm-lit \
      ..

make -j16
make check
```
 script Reference: https://flang.llvm.org/docs/FortranLLVMTestSuite.html

the result of the Fortran test form llvm-test-suite have not changed.
<img width="392" height="122" alt="image" src="https://github.com/user-attachments/assets/f1ccdce1-ab8c-409e-b56f-63fdd6c32756" />



https://github.com/llvm/llvm-project/pull/174915