wrappers: Skip the clang-scan-deps wrapper script on Unix

The wrapper script no longer has any purpose on Unix.

Just do a plain symlink to the clang-scan-deps tool.

On Windows, the wrapper executable still is used to inject a
default -target option, if the executable name doesn't contain
a triple.

install-wrappers.sh

@@ -142,16 +142,18 @@ 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
     for target_os in $TARGET_OSES; do
         for exec in clang clang++ gcc g++ c++ as; do
             ln -sf clang-target-wrapper$CTW_SUFFIX $arch-w64-$target_os-$exec$CTW_LINK_SUFFIX
         done
-        ln -sf clang-scan-deps-wrapper$CTW_SUFFIX $arch-w64-$target_os-clang-scan-deps$CTW_LINK_SUFFIX
+        ln -sf $CSDW $arch-w64-$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