This happens with `tinygo test` for example when testing multiple
packages at the same time. I found this because the compiler crashed in
`make tinygo-test-fast`:
fatal error: concurrent map writes
fatal error: concurrent map read and map write
goroutine 15 [running]:
github.com/tinygo-org/tinygo/builder.Build({0x40002d0be0, 0xa}, {0x0, 0x0}, {0x4000398048, 0x14}, 0x40003b0000)
/home/ayke/src/tinygo/tinygo/builder/build.go:131 +0x388
main.buildAndRun({0x40002d0be0, 0xa}, 0x40003b0000, {0x8bc178, 0x40003a4090}, {0x0, 0x0, 0x0}, {0x0, 0x0, ...}, ...)
/home/ayke/src/tinygo/tinygo/main.go:856 +0x45c
main.Test({0x40002d0be0, 0xa}, {0x8bc118, 0x40000b3a08}, {0x0?, 0x0?}, 0x40001e6000, {0x0, 0x0})
/home/ayke/src/tinygo/tinygo/main.go:270 +0x758
main.main.func3()
/home/ayke/src/tinygo/tinygo/main.go:1718 +0xe4
created by main.main in goroutine 1
/home/ayke/src/tinygo/tinygo/main.go:1712 +0x34ec
My solution is essentially to copy the map over instead of modifying it
directly.
I've also moved the code up a little, because I think that's a more
sensible place (out of the way of the whole package compile logic).
8cbfbcae5a