arm-musl: set max_atomic_width

src/librustc_back/target/arm_unknown_linux_musleabi.rs

@@ -16,6 +16,7 @@ pub fn target() -> Target {
     // Most of these settings are copied from the arm_unknown_linux_gnueabi
     // target.
     base.features = "+v6".to_string();
+    base.max_atomic_width = 64;
     Target {
         // It's important we use "gnueabi" and not "musleabi" here. LLVM uses it
         // to determine the calling convention and float ABI, and it doesn't

src/librustc_back/target/arm_unknown_linux_musleabihf.rs

@@ -16,6 +16,7 @@ pub fn target() -> Target {
     // Most of these settings are copied from the arm_unknown_linux_gnueabihf
     // target.
     base.features = "+v6,+vfp2".to_string();
+    base.max_atomic_width = 64;
     Target {
         // It's important we use "gnueabihf" and not "musleabihf" here. LLVM
         // uses it to determine the calling convention and float ABI, and it

src/librustc_back/target/armv7_unknown_linux_musleabihf.rs

@@ -17,6 +17,7 @@ pub fn target() -> Target {
     // target.
     base.features = "+v7,+vfp3,+neon".to_string();
     base.cpu = "cortex-a8".to_string();
+    base.max_atomic_width = 64;
     Target {
         // It's important we use "gnueabihf" and not "musleabihf" here. LLVM
         // uses it to determine the calling convention and float ABI, and LLVM