libgo: fix for runtime/check failure with "-O0 -g"

    
    Tweak the makefile rules for the runtime/check test to
    insure that the runtime package is compiled with
    "-fgo-compiling-runtime". This resolves a test failure
    (unsat on runtime.getcallerpc) when in a build directory where the
    compiler flags have been configured to disable optimization.
    
    Reviewed-on: https://go-review.googlesource.com/30010

From-SVN: r240588