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

install-wrappers.sh

@@ -123,10 +123,6 @@ fi
 
 mkdir -p "$PREFIX/bin"
 cp wrappers/*-wrapper.sh "$PREFIX/bin"
-cp wrappers/mingw32-common.cfg $PREFIX/bin
-for arch in $ARCHS; do
-    cp wrappers/$arch-w64-windows-gnu.cfg $PREFIX/bin
-done
 if [ -n "$HOST" ] && [ -n "$EXEEXT" ]; then
     # TODO: If building natively on msys, pick up the default HOST value from there.
     WRAPPER_FLAGS="$WRAPPER_FLAGS -DDEFAULT_TARGET=\"$HOST\""
@@ -142,10 +138,8 @@ if [ -n "$EXEEXT" ]; then
     # when invoked from outside of MSYS.
     CTW_SUFFIX=$EXEEXT
     CTW_LINK_SUFFIX=$EXEEXT
-    CSDW=clang-scan-deps-wrapper$EXEEXT
 else
     CTW_SUFFIX=.sh
-    CSDW=clang-scan-deps
 fi
 cd "$PREFIX/bin"
 for arch in $ARCHS; do
@@ -153,7 +147,7 @@ for arch in $ARCHS; do
         for exec in clang clang++ gcc g++ c++ as; do
             ln -sf clang-target-wrapper$CTW_SUFFIX $arch-w64-$target_os-$exec$CTW_LINK_SUFFIX
         done
-        ln -sf $CSDW $arch-w64-$target_os-clang-scan-deps$CTW_LINK_SUFFIX
+        ln -sf clang-scan-deps-wrapper$CTW_SUFFIX $arch-w64-$target_os-clang-scan-deps$CTW_LINK_SUFFIX
         for exec in addr2line ar ranlib nm objcopy readelf size strings strip llvm-ar llvm-ranlib; do
             if [ -n "$EXEEXT" ]; then
                 link_target=llvm-wrapper