Fix compiling binaries with go 1.13

The go compile command in go 1.13 needs -p main instead of
-p $pkgPath when compiling binaries.  This also works for older
go releases.

Also turn on travis for go 1.13.

Change-Id: I45ce185aa44cfa01a7933cc6e52290a85c851641

.travis.yml

@@ -4,6 +4,7 @@ go:
     - "1.10"
     - "1.11"
     - "1.12"
+    - "1.13"
 
 cache:
     directories:

bootstrap/bootstrap.go

@@ -437,7 +437,7 @@ func (g *goBinary) GenerateBuildActions(ctx blueprint.ModuleContext) {
 			name, srcs, genSrcs, testSrcs)
 	}
 
-	buildGoPackage(ctx, objDir, name, archiveFile, srcs, genSrcs)
+	buildGoPackage(ctx, objDir, "main", archiveFile, srcs, genSrcs)
 
 	var linkDeps []string
 	var libDirFlags []string