Update based on @alex's PR

Author: Gelbpunkt

src/ci/docker/host-x86_64/dist-various-1/Dockerfile

@@ -84,10 +84,6 @@ RUN env \
     CXX=arm-linux-gnueabihf-g++ CXXFLAGS="-march=armv7-a" \
     bash musl.sh armv7hf && \
     env \
-    CC=aarch64-linux-gnu-gcc \
-    CXX=aarch64-linux-gnu-g++ \
-    bash musl.sh aarch64 && \
-    env \
     CC=mips-openwrt-linux-gcc \
     CXX=mips-openwrt-linux-g++ \
     bash musl.sh mips && \
@@ -130,7 +126,6 @@ ENV TARGETS=$TARGETS,arm-unknown-linux-musleabihf
 ENV TARGETS=$TARGETS,armv5te-unknown-linux-gnueabi
 ENV TARGETS=$TARGETS,armv5te-unknown-linux-musleabi
 ENV TARGETS=$TARGETS,armv7-unknown-linux-musleabihf
-ENV TARGETS=$TARGETS,aarch64-unknown-linux-musl
 ENV TARGETS=$TARGETS,aarch64-unknown-none
 ENV TARGETS=$TARGETS,aarch64-unknown-none-softfloat
 ENV TARGETS=$TARGETS,sparc64-unknown-linux-gnu
@@ -185,7 +180,6 @@ ENV RUST_CONFIGURE_ARGS \
       --musl-root-arm=/musl-arm \
       --musl-root-armhf=/musl-armhf \
       --musl-root-armv7hf=/musl-armv7hf \
-      --musl-root-aarch64=/musl-aarch64 \
       --musl-root-mips=/musl-mips \
       --musl-root-mipsel=/musl-mipsel \
       --musl-root-mips64=/musl-mips64 \

src/doc/rustc/src/platform-support.md

@@ -62,7 +62,7 @@ target | std | host | notes
 `aarch64-linux-android` | ✓ |  | ARM64 Android
 `aarch64-pc-windows-msvc` | ✓ |  | ARM64 Windows MSVC
 `aarch64-unknown-linux-gnu` | ✓ | ✓ | ARM64 Linux (kernel 4.2, glibc 2.17)
-`aarch64-unknown-linux-musl` | ✓ |  | ARM64 Linux with MUSL
+`aarch64-unknown-linux-musl` | ✓ | ✓ | ARM64 Linux with MUSL
 `aarch64-unknown-none` | * |  | Bare ARM64, hardfloat
 `aarch64-unknown-none-softfloat` | * |  | Bare ARM64, softfloat
 `arm-linux-androideabi` | ✓ |  | ARMv7 Android