Revert "Add ARM64X support"

This reverts commit 64effa9a71.

It turns out that the LLD handling of the TLS data structures
("_tls_used" and "_tls_index") needs more work, causing the
arm64ec side of arm64x binaries to not get them hooked up properly.

build-mingw-w64.sh

@@ -105,10 +105,6 @@ $MAKE install
 cd ../..
 if [ -z "$SKIP_INCLUDE_TRIPLET_PREFIX" ]; then
     for arch in $ARCHS; do
-        case $arch in
-        arm64ec) continue ;;
-        esac
-
         mkdir -p "$PREFIX/$arch-w64-mingw32"
         if [ ! -e "$PREFIX/$arch-w64-mingw32/include" ]; then
             ln -sfn ../generic-w64-mingw32/include "$PREFIX/$arch-w64-mingw32/include"
@@ -116,24 +112,17 @@ if [ -z "$SKIP_INCLUDE_TRIPLET_PREFIX" ]; then
     done
 fi
 
-ARM64X_FLAGS=""
-for arch in $ARCHS; do
-    case $arch in
-    arm64ec) ARM64X_FLAGS="--enable-arm64x" ;;
-    esac
-done
-
 cd mingw-w64-crt
 for arch in $ARCHS; do
+    [ -z "$CLEAN" ] || rm -rf build-$arch
+    mkdir -p build-$arch
+    cd build-$arch
     case $arch in
     armv7)
         FLAGS="--disable-lib32 --disable-lib64 --enable-libarm32"
         ;;
-    aarch64)
-        FLAGS="--disable-lib32 --disable-lib64 --enable-libarm64 $ARM64X_FLAGS"
-        ;;
-    arm64ec)
-        continue
+    aarch64|arm64ec)
+        FLAGS="--disable-lib32 --disable-lib64 --enable-libarm64"
         ;;
     i686)
         FLAGS="--enable-lib32 --disable-lib64"
@@ -144,9 +133,6 @@ for arch in $ARCHS; do
     esac
     FLAGS="$FLAGS --with-default-msvcrt=$DEFAULT_MSVCRT"
     FLAGS="$FLAGS --enable-silent-rules"
-    [ -z "$CLEAN" ] || rm -rf build-$arch
-    mkdir -p build-$arch
-    cd build-$arch
     ../configure --host=$arch-w64-mingw32 --prefix="$PREFIX/$arch-w64-mingw32" $FLAGS $CFGUARD_FLAGS $CRT_CONFIG_FLAGS
     $MAKE -j$CORES
     $MAKE install
@@ -155,10 +141,6 @@ done
 cd ..
 
 for arch in $ARCHS; do
-    case $arch in
-    arm64ec) continue ;;
-    esac
-
     if [ ! -f $PREFIX/$arch-w64-mingw32/lib/libssp.a ]; then
         # Create empty dummy archives, to avoid failing when the compiler
         # driver adds "-lssp -lssh_nonshared" when linking.