Allow remote execution of link actions.

This CL adds a remoteexec package that allows adding a configurable RBE
prefix to the template.

Test: built aosp crosshatch userdebug with and without RBE_CXX_LINKS.
Change-Id: Ica920c3d7f79f2996210b9cbd448126451c1707c
diff --git a/remoteexec/remoteexec_test.go b/remoteexec/remoteexec_test.go
new file mode 100644
index 0000000..30e891c
--- /dev/null
+++ b/remoteexec/remoteexec_test.go
@@ -0,0 +1,83 @@
+// Copyright 2020 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package remoteexec
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestTemplate(t *testing.T) {
+	tests := []struct {
+		name   string
+		params *REParams
+		want   string
+	}{
+		{
+			name: "basic",
+			params: &REParams{
+				Labels:      map[string]string{"type": "compile", "lang": "cpp", "compiler": "clang"},
+				Inputs:      []string{"$in"},
+				OutputFiles: []string{"$out"},
+				Platform: map[string]string{
+					ContainerImageKey: DefaultImage,
+					PoolKey:           "default",
+				},
+			},
+			want: fmt.Sprintf("${remoteexec.Wrapper} --labels=compiler=clang,lang=cpp,type=compile --platform=\"Pool=default,container-image=%s\" --exec_strategy=local --inputs=$in --output_files=$out -- ", DefaultImage),
+		},
+		{
+			name: "all params",
+			params: &REParams{
+				Labels:          map[string]string{"type": "compile", "lang": "cpp", "compiler": "clang"},
+				Inputs:          []string{"$in"},
+				OutputFiles:     []string{"$out"},
+				ExecStrategy:    "remote",
+				RSPFile:         "$out.rsp",
+				ToolchainInputs: []string{"clang++"},
+				Platform: map[string]string{
+					ContainerImageKey: DefaultImage,
+					PoolKey:           "default",
+				},
+			},
+			want: fmt.Sprintf("${remoteexec.Wrapper} --labels=compiler=clang,lang=cpp,type=compile --platform=\"Pool=default,container-image=%s\" --exec_strategy=remote --inputs=$in --input_list_paths=$out.rsp --output_files=$out --toolchain_inputs=clang++ -- ", DefaultImage),
+		},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			if got := test.params.Template(); got != test.want {
+				t.Errorf("Template() returned\n%s\nwant\n%s", got, test.want)
+			}
+		})
+	}
+}
+
+func TestTemplateDeterminism(t *testing.T) {
+	r := &REParams{
+		Labels:      map[string]string{"type": "compile", "lang": "cpp", "compiler": "clang"},
+		Inputs:      []string{"$in"},
+		OutputFiles: []string{"$out"},
+		Platform: map[string]string{
+			ContainerImageKey: DefaultImage,
+			PoolKey:           "default",
+		},
+	}
+	want := fmt.Sprintf("${remoteexec.Wrapper} --labels=compiler=clang,lang=cpp,type=compile --platform=\"Pool=default,container-image=%s\" --exec_strategy=local --inputs=$in --output_files=$out -- ", DefaultImage)
+	for i := 0; i < 1000; i++ {
+		if got := r.Template(); got != want {
+			t.Fatalf("Template() returned\n%s\nwant\n%s", got, want)
+		}
+	}
+}