[openmp-offload-amdgpu-clang-flang] Re-add FLANG_RUNTIME_F128_MATH_LIB (#407)

The option was removed in #395. After
llvm/llvm-project#130411, the option should now
work even when compiling flang-rt with Clang.

Author: Meinersbur

buildbot/osuosl/master/config/builders.py

@@ -2077,6 +2077,7 @@
                             "-DLLVM_ENABLE_ASSERTIONS=ON",
                             "-DCMAKE_C_COMPILER_LAUNCHER=ccache",
                             "-DCMAKE_CXX_COMPILER_LAUNCHER=ccache",
+                            "-DFLANG_RUNTIME_F128_MATH_LIB=libquadmath",
                             "-DLLVM_ENABLE_PER_TARGET_RUNTIME_DIR=ON",
                             "-DCMAKE_CXX_STANDARD=17",
                             "-DBUILD_SHARED_LIBS=ON",