apple: build.sh: fix compilation for arm64

With latest SDK, arm64 is returned as architecture name for aarch64
machine targets from Apple, which is not recognized by autoconf, and
breaks compilation of multiple contribs.

We still need to indicate that we want an arm64 SDK, but replace arm64
by aarch64 in build triplets until autoconf fixes this.

extras/package/apple/build.sh

@@ -233,6 +233,7 @@ set_host_triplet()
     # Therefore we construct a triplet here without a version number, which
     # will not match the autoconf "guessed" host machine triplet.
     VLC_HOST_TRIPLET="${triplet_arch}-apple-darwin"
+    VLC_HOST_TRIPLET="${VLC_HOST_TRIPLET/arm64/aarch64}"
 }
 
 # Set the VLC_BUILD_TRIPLET based on the architecture
@@ -244,7 +245,8 @@ set_host_triplet()
 set_build_triplet()
 {
     local build_arch="$(uname -m | cut -d. -f1)"
-    VLC_BUILD_TRIPLET="$(cc -arch "${build_arch}" -dumpmachine)"
+    VLC_BUILD_TRIPLET="$(${VLC_HOST_CC} -arch "${build_arch}" -dumpmachine)"
+    VLC_BUILD_TRIPLET="${VLC_BUILD_TRIPLET/arm64/aarch64}"
 }
 
 # Take SDK name, verify it exists and populate