Add dist support to Soong

When dist'ing a library or binary that has use_version_lib set, always
distribute the stamped version, even for the device.

Test: m test_build_version_test dist
Change-Id: I2995ec516b1d182ce18f099aeaa4d186ffbcf01f

cc/libbuildversion/libbuildversion.cpp

@@ -23,9 +23,19 @@
 namespace android {
 namespace build {
 
+#define PLACEHOLDER "SOONG BUILD NUMBER PLACEHOLDER"
+
+extern "C" {
+  char soong_build_number[128] = PLACEHOLDER;
+}
+
 #ifdef __ANDROID__
 
 std::string GetBuildNumber() {
+  if (strcmp(PLACEHOLDER, soong_build_number) != 0) {
+    return soong_build_number;
+  }
+
   const prop_info* pi = __system_property_find("ro.build.version.incremental");
   if (pi == nullptr) return "";
 
@@ -42,10 +52,6 @@ std::string GetBuildNumber() {
 
 #else
 
-extern "C" {
-  char soong_build_number[128] = "SOONG BUILD NUMBER PLACEHOLDER";
-}
-
 std::string GetBuildNumber() {
   return soong_build_number;
 }