dashboard: update illumos $PATH to include gcc

This fixes errors such as:
https://build.golang.org/log/b870c4ed812edba58cf7a35718672d1424f9fd8a

Updates golang/go#32308

Change-Id: I231b9662c556b2b0044d5a88c61e8c6231f2df86
Reviewed-on: https://go-review.googlesource.com/c/build/+/179618
Reviewed-by: Dmitri Shuralyov <[email protected]>

Author: bradfitz

dashboard/builders.go

@@ -452,7 +452,11 @@ var Hosts = map[string]*HostConfig{
 		Notes:     "run by Go team on Joyent, on a SmartOS 'infrastructure container'",
 		IsReverse: true,
 		ExpectNum: 1,
-		env:       []string{"GOROOT_BOOTSTRAP=/root/goboot", "HOME=/root"},
+		env: []string{
+			"GOROOT_BOOTSTRAP=/root/goboot",
+			"HOME=/root",
+			"PATH=/usr/sbin:/usr/bin:/opt/local/bin", // gcc is in /opt/local/bin
+		},
 	},
 	"host-solaris-oracle-amd64-oraclerel": &HostConfig{
 		Notes:       "Oracle Solaris amd64 Release System",