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-libraries.sh

@@ -55,36 +55,18 @@ if command -v gmake >/dev/null; then
     MAKE=gmake
 fi
 
-ARM64X_FLAGS=""
-for arch in $ARCHS; do
-    case $arch in
-    arm64ec) ARM64X_FLAGS="-marm64x" ;;
-    esac
-done
-
 cd mingw-w64/mingw-w64-libraries
 for lib in winpthreads winstorecompat; do
     cd $lib
-    FLAGS=""
     for arch in $ARCHS; do
-        case $arch in
-        aarch64)
-            FLAGS="$ARM64X_FLAGS"
-            ;;
-        arm64ec)
-            continue
-            ;;
-        esac
-
         [ -z "$CLEAN" ] || rm -rf build-$arch
         mkdir -p build-$arch
         cd build-$arch
         arch_prefix="$PREFIX/$arch-w64-mingw32"
         ../configure --host=$arch-w64-mingw32 --prefix="$arch_prefix" --libdir="$arch_prefix/lib" \
             --enable-silent-rules \
-            CFLAGS="$USE_CFLAGS $FLAGS" \
-            CXXFLAGS="$USE_CFLAGS $FLAGS" \
-            LDFLAGS="$FLAGS"
+            CFLAGS="$USE_CFLAGS" \
+            CXXFLAGS="$USE_CFLAGS"
         $MAKE -j$CORES
         $MAKE install
         cd ..