Revert use of Clang config files

This reverts commit 49db4a3a15,
9f1f0104f1,
4f95c14adf,
c34dc64028,
570fdcd251,
4bff0298c5 and
6939aee0c0.

When relying on Clang config files, two issues appeared:

- Running the compiler-rt tests fails, because the compiler-rt tests
  disable any default config files, breaking the compiler
  in this case:
  https://github.com/llvm/llvm-project/blob/llvmorg-19.1.1/compiler-rt/test/lit.common.cfg.py#L983

- Wine fails to build using llvm-mingw as cross compiler, because
  Wine adds the --no-default-config flag to Clang while compiling,
  if supported:
  https://gitlab.winehq.org/wine/wine/-/blob/wine-9.19/configure.ac?ref_type=tags#L866-868
  This causes llvm-mingw to omit the -rtlib=compiler-rt option
  (specified in a config file), making the compiler look for libgcc
  instead. Doing a check to see that linking succeeds doesn't necessarily
  help here - such a check already exists, but it tests linking with
  -nostdlib -nodefaultlibs:
  https://gitlab.winehq.org/wine/wine/-/blob/wine-9.19/aclocal.m4?ref_type=tags#L193-L206

Dockerfile

@@ -24,7 +24,7 @@ ARG CFGUARD_ARGS=--enable-cfguard
 
 # Build everything that uses the llvm monorepo. We need to build the mingw runtime before the compiler-rt/libunwind/libcxxabi/libcxx runtimes.
 COPY build-llvm.sh build-lldb-mi.sh strip-llvm.sh install-wrappers.sh build-mingw-w64.sh build-mingw-w64-tools.sh build-compiler-rt.sh build-libcxx.sh build-mingw-w64-libraries.sh build-openmp.sh ./
-COPY wrappers/*.sh wrappers/*.c wrappers/*.h wrappers/*.cfg ./wrappers/
+COPY wrappers/*.sh wrappers/*.c wrappers/*.h ./wrappers/
 RUN ./build-llvm.sh $TOOLCHAIN_PREFIX && \
     ./build-lldb-mi.sh $TOOLCHAIN_PREFIX && \
     ./strip-llvm.sh $TOOLCHAIN_PREFIX && \