ng: testing with -race confuses plugin

[sbinet]

with go1.10beta1, the following fails:

$> go test -race ./eval
--- FAIL: TestPrograms (7.69s)
    --- FAIL: TestPrograms/array1 (0.45s)
    	eval_test.go:212: neugram panic: plugin: failed to open Go package "md5": plugin.Open("/tmp/ng-tmp-706103538/ng-plugin-crypto_md5"): plugin was built with a different version of package runtime
    --- FAIL: TestPrograms/http1 (2.27s)
    	eval_test.go:212: neugram panic: plugin: failed to open Go package "http": plugin.Open("/tmp/ng-tmp-711797768/ng-plugin-net_http"): plugin was built with a different version of package runtime
    --- FAIL: TestPrograms/import4 (1.07s)
    	eval_test.go:212: neugram panic: plugin: failed to open Go package "ioutil": plugin.Open("/tmp/ng-tmp-307738800/ng-plugin-io_ioutil"): plugin was built with a different version of package runtime
    --- FAIL: TestPrograms/import5 (0.66s)
    	eval_test.go:212: neugram panic: plugin: failed to open Go package "md5": plugin.Open("/tmp/ng-tmp-641257314/ng-plugin-crypto_md5"): plugin was built with a different version of package runtime
    --- FAIL: TestPrograms/import6 (0.56s)
    	eval_test.go:212: neugram panic: plugin: failed to open Go package "frame": plugin.Open("/tmp/ng-tmp-817640164/ng-plugin-neugram.io_ng_frame"): plugin was built with a different version of package runtime
FAIL
FAIL	neugram.io/ng/eval	7.720s

I guess gowrap needs to somehow detect it needs to build the plugin with -race