build-compiler-rt: Stop setting CMAKE_*_COMPILER_WORKS

Since 8368e4d54c459fe173d76277f17c632478e91add in llvm-project (pushed
on March 11 2021), the lib/builtins CMakeLists.txt sets
CMAKE_TRY_COMPILE_TARGET_TYPE to STATIC_LIBRARY, which makes the
compiler tests pass before the toolchain is fully functional, by not
doing linking tests.

build-compiler-rt.sh

@@ -103,8 +103,6 @@ for arch in $ARCHS; do
         -DCMAKE_SYSTEM_NAME=Windows \
         -DCMAKE_AR="$PREFIX/bin/llvm-ar" \
         -DCMAKE_RANLIB="$PREFIX/bin/llvm-ranlib" \
-        -DCMAKE_C_COMPILER_WORKS=1 \
-        -DCMAKE_CXX_COMPILER_WORKS=1 \
         -DCMAKE_C_COMPILER_TARGET=$arch-windows-gnu \
         -DCOMPILER_RT_DEFAULT_TARGET_ONLY=TRUE \
         -DCOMPILER_RT_USE_BUILTINS_LIBRARY=TRUE \