Include arm64ec in the lists of all architectures

Since LLVM 21.x, the upstream support for ARM64EC in LLD and
compiler-rt is complete enough for us to be able to build it.

install-wrappers.sh

@@ -42,7 +42,7 @@ fi
 mkdir -p "$PREFIX"
 PREFIX="$(cd "$PREFIX" && pwd)"
 
-: ${ARCHS:=${TOOLCHAIN_ARCHS-i686 x86_64 armv7 aarch64}}
+: ${ARCHS:=${TOOLCHAIN_ARCHS-i686 x86_64 armv7 aarch64 arm64ec}}
 : ${TARGET_OSES:=${TOOLCHAIN_TARGET_OSES-mingw32 mingw32uwp}}
 
 if [ -n "$HOST" ] && [ -z "$CC" ]; then