Fix building only certain architectures when building on windows

On windows, we rename clang.exe to clang-$MAJOR.exe, and later
install clang.exe as a wrapper for the default architecture. But
if only building certain architectures, and the host architecture
isn't one of them, we shouldn't install any unprefixed clang.exe at
all.

build-compiler-rt.sh

@@ -29,7 +29,8 @@ export PATH="$PREFIX/bin:$PATH"
 : ${CORES:=4}
 : ${ARCHS:=${TOOLCHAIN_ARCHS-i686 x86_64 armv7 aarch64}}
 
-CLANG_VERSION=$(basename "$(dirname "$(dirname "$(dirname "$("$PREFIX/bin/clang" --print-libgcc-file-name -rtlib=compiler-rt)")")")")
+ANY_ARCH=$(echo $ARCHS | awk '{print $1}')
+CLANG_VERSION=$(basename "$(dirname "$(dirname "$(dirname "$("$PREFIX/bin/$ANY_ARCH-w64-mingw32-clang" --print-libgcc-file-name -rtlib=compiler-rt)")")")")
 
 if [ ! -d llvm-project/compiler-rt ] || [ -n "$SYNC" ]; then
     CHECKOUT_ONLY=1 ./build-llvm.sh

build-mingw-w64.sh

@@ -156,8 +156,10 @@ if [ -n "$SKIP_INCLUDE_TRIPLET_PREFIX" ]; then
     done
 fi
 if [ -n "$EXEEXT" ]; then
-    if [ -z "$HOST" ]; then
+    if [ -z "$HOST" ] && [ -f clang$EXEEXT ]; then
         HOST=$(./clang -dumpmachine | sed 's/-.*//')-w64-mingw32
     fi
-    ln -sf $HOST-widl$EXEEXT widl$EXEEXT
+    if [ -n "$HOST" ]; then
+        ln -sf $HOST-widl$EXEEXT widl$EXEEXT
+    fi
 fi

install-wrappers.sh

@@ -94,10 +94,17 @@ if [ -n "$EXEEXT" ]; then
     if [ -z "$HOST" ]; then
         HOST=$(./clang-$CLANG_MAJOR -dumpmachine | sed 's/-.*//')-w64-mingw32
     fi
-    for exec in clang clang++ gcc g++ cc c99 c11 c++ addr2line ar ranlib nm objcopy strings strip windres; do
-        ln -sf $HOST-$exec$EXEEXT $exec$EXEEXT
-    done
-    for exec in ld objdump dlltool; do
-        ln -sf $HOST-$exec $exec
-    done
+    HOST_ARCH="${HOST%%-*}"
+    # Install unprefixed wrappers if $HOST is one of the architectures
+    # we are installing wrappers for.
+    case $ARCHS in
+    *$HOST_ARCH*)
+        for exec in clang clang++ gcc g++ cc c99 c11 c++ addr2line ar ranlib nm objcopy strings strip windres; do
+            ln -sf $HOST-$exec$EXEEXT $exec$EXEEXT
+        done
+        for exec in ld objdump dlltool; do
+            ln -sf $HOST-$exec $exec
+        done
+        ;;
+    esac
 fi