1. Fix cross build bug for aarch64 with simd-accel

2. Set -march=armv8-a as default value for aarch64
3. Enable aarch64 + simd-accel for Android build

Author: kings-way

build.rs

@@ -155,7 +155,7 @@ fn write_tables() {
     feature = "simd-accel",
     any(target_arch = "x86_64", target_arch = "aarch64"),
     not(target_env = "msvc"),
-    not(any(target_os = "android", target_os = "ios"))
+    not(any(target_os = "ios"))
 ))]
 fn compile_simd_c() {
     let mut build = cc::Build::new();
@@ -169,8 +169,11 @@ fn compile_simd_c() {
         Err(_error) => {
             // On x86-64 enabling Haswell architecture unlocks useful instructions and improves performance
             // dramatically while allowing it to run ony modern CPU.
-            #[cfg(target_arch = "x86_64")]
-            build.flag(&"-march=haswell");
+            match env::var("CARGO_CFG_TARGET_ARCH").unwrap().as_str(){
+                "x86_64"  => drop(build.flag(&"-march=haswell")),
+                "aarch64" => drop(build.flag(&"-march=armv8-a")),
+                _         => ()
+            }
         }
     }
 
@@ -184,7 +187,7 @@ fn compile_simd_c() {
     feature = "simd-accel",
     any(target_arch = "x86_64", target_arch = "aarch64"),
     not(target_env = "msvc"),
-    not(any(target_os = "android", target_os = "ios"))
+    not(any(target_os = "ios"))
 )))]
 fn compile_simd_c() {}