Read the proc status file when PID is given for metrics purpose.

To measure the MaxRSS memory correctly, read the proc status file
under /proc/<pid>/status and extract the MaxRSS value from it. The
implementation is only available for Linux based distributions.

Bug: b/169453825
Test: go test
Change-Id: I32e3068fee7447f9ef5dfb5a8d8dcb6934e0af23
diff --git a/ui/metrics/proc/Android.bp b/ui/metrics/proc/Android.bp
new file mode 100644
index 0000000..32d8217
--- /dev/null
+++ b/ui/metrics/proc/Android.bp
@@ -0,0 +1,37 @@
+// 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.
+
+bootstrap_go_package {
+    name: "soong-ui-metrics-proc",
+    pkgPath: "android/soong/ui/metrics/proc",
+    deps: [
+        "soong-finder-fs",
+    ],
+    srcs: [
+        "status.go",
+    ],
+    linux: {
+        srcs: [
+            "status_linux.go",
+        ],
+        testSrcs: [
+            "status_linux_test.go",
+        ],
+    },
+    darwin: {
+        srcs: [
+            "status_darwin.go",
+        ],
+    },
+}