Add snowflake pt to alpha linux builds
Please see the attached.
Reproducibility of cgo depends on a compiler that supports,
-gno-record-gcc-switches
-fdebug-prefix-map=$WORK=/tmp/go-build
which landed in go 1.7.3
(see https://github.com/golang/go/commit/5bbb98df0960f57dca73cb7640456608d4cc0917)