When building a go binary that's linking against some .so/.a, while
cross-compiling, we need to pass the correct compiler, otherwise
`go build` will fail with the not-so helpful error message:
```
gcc_arm64.S: Assembler messages:
gcc_arm64.S:28: Error: no such instruction: `stp x29,x30,[sp,'
gcc_arm64.S:32: Error: too many memory references for `mov'
gcc_arm64.S:34: Error: no such instruction: `stp x19,x20,[sp,'
gcc_arm64.S:37: Error: no such instruction: `stp x21,x22,[sp,'
gcc_arm64.S:40: Error: no such instruction: `stp x23,x24,[sp,'
gcc_arm64.S:43: Error: no such instruction: `stp x25,x26,[sp,'
gcc_arm64.S:46: Error: no such instruction: `stp x27,x28,[sp,'
gcc_arm64.S:50: Error: too many memory references for `mov'
gcc_arm64.S:51: Error: too many memory references for `mov'
gcc_arm64.S:52: Error: too many memory references for `mov'
gcc_arm64.S:54: Error: no such instruction: `blr x20'
gcc_arm64.S:55: Error: no such instruction: `blr x19'
gcc_arm64.S:57: Error: no such instruction: `ldp x27,x28,[sp,'
gcc_arm64.S:60: Error: no such instruction: `ldp x25,x26,[sp,'
gcc_arm64.S:63: Error: no such instruction: `ldp x23,x24,[sp,'
gcc_arm64.S:66: Error: no such instruction: `ldp x21,x22,[sp,'
gcc_arm64.S:69: Error: no such instruction: `ldp x19,x20,[sp,'
gcc_arm64.S:72: Error: no such instruction: `ldp x29,x30,[sp],'
```
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