Only set TARGET_PLATFORM version in lunch when explicitly requested

Setting TARGET_PLATFORM_VERSION to DEFAULT_PLATFORM_VERSION during
"lunch sailfish-userdebug" causes unnecessary pain when
DEFAULT_PLATFORM_VERSION becomes invalid after branching.  Only
set TARGET_PLATFORM_VERSION if it was explicitly requested with
lunch sailfish-userdebug-OPR1.

Test: build/make/tests/envsetup_tests.sh
Bug: 34972208
Bug: 37208937
Change-Id: I40ba4617e73803c5bec1a8d317382f70fb3ec3a2
Merged-In: I40ba4617e73803c5bec1a8d317382f70fb3ec3a2
diff --git a/core/version_defaults.mk b/core/version_defaults.mk
index ba07200..5a89fc9 100644
--- a/core/version_defaults.mk
+++ b/core/version_defaults.mk
@@ -49,6 +49,12 @@
 
 ifndef TARGET_PLATFORM_VERSION
   TARGET_PLATFORM_VERSION := $(DEFAULT_PLATFORM_VERSION)
+else ifeq ($(TARGET_PLATFORM_VERSION),OPR1)
+  # HACK: lunch currently sets TARGET_PLATFORM_VERSION to
+  # DEFAULT_PLATFORM_VERSION, which causes unnecessary pain
+  # when the old DEFAULT_PLATFORM_VERSION becomes invalid.
+  # For now, silently upgrade OPR1 to the current default.
+  TARGET_PLATFORM_VERSION := $(DEFAULT_PLATFORM_VERSION)
 endif
 
 ifeq (,$(filter $(ALLOWED_VERSIONS), $(TARGET_PLATFORM_VERSION)))