[tests] Improve test Makefile when specifying runtime identifier on t…

…he command line. (#21169)

Using RUNTIMEIDENTIFIER(S) in the Makefile interferes with the build, because
they get passed on to msbuild, which sees them as properties (RuntimeIdentifier(s)).

Thus use RID instead, and only pass on the value to the build if appropriate.

tests/common/shared-dotnet.mk

@@ -72,44 +72,50 @@ ifeq ($(PLATFORM),)
 PLATFORM=$(shell basename "$(CURDIR)")
 endif
 
-ifeq ($(RUNTIMEIDENTIFIERS),)
+ifneq ($(RUNTIMEIDENTIFIERS)$(RUNTIMEIDENTIFIER),)
+$(error "Don't set RUNTIMEIDENTIFIER or RUNTIMEIDENTIFIERS, set RID instead")
+endif
+
+ifeq ($(RID),)
 ifeq ($(PLATFORM),iOS)
-RUNTIMEIDENTIFIERS=ios-arm64
+RID=ios-arm64
 else ifeq ($(PLATFORM),tvOS)
-RUNTIMEIDENTIFIERS=tvos-arm64
+RID=tvos-arm64
 else ifeq ($(PLATFORM),MacCatalyst)
 ifeq ($(CONFIG),Release)
-RUNTIMEIDENTIFIERS=maccatalyst-x64;maccatalyst-arm64
+RID=maccatalyst-x64;maccatalyst-arm64
 else ifneq ($(UNIVERSAL),)
-RUNTIMEIDENTIFIERS=maccatalyst-x64;maccatalyst-arm64
+RID=maccatalyst-x64;maccatalyst-arm64
 else ifeq ($(shell arch),arm64)
-RUNTIMEIDENTIFIERS=maccatalyst-arm64
+RID=maccatalyst-arm64
 else
-RUNTIMEIDENTIFIERS=maccatalyst-x64
+RID=maccatalyst-x64
 endif
 else ifeq ($(PLATFORM),macOS)
 ifeq ($(CONFIG),Release)
-RUNTIMEIDENTIFIERS=osx-x64;osx-arm64
+RID=osx-x64;osx-arm64
 else ifneq ($(UNIVERSAL),)
-RUNTIMEIDENTIFIERS=osx-x64;osx-arm64
+RID=osx-x64;osx-arm64
 else ifeq ($(shell arch),arm64)
-RUNTIMEIDENTIFIERS=osx-arm64
+RID=osx-arm64
 else
-RUNTIMEIDENTIFIERS=osx-x64
+RID=osx-x64
 endif
 else
-RUNTIMEIDENTIFIERS=unknown-platform-$(PLATFORM)
+RID=unknown-platform-$(PLATFORM)
 endif
 endif
 
 ifneq ($(UNIVERSAL),)
 UNIVERSAL_ARGUMENT=/p:UniversalBuild=true
 endif
 
-ifeq ($(findstring ;,$(RUNTIMEIDENTIFIERS)),;)
+ifeq ($(findstring ;,$(RID)),;)
 PATH_RID=
+export RUNTIMEIDENTIFIERS=$(RID)
 else
-PATH_RID=$(RUNTIMEIDENTIFIERS)/
+PATH_RID=$(RID)/
+export RUNTIMEIDENTIFIER=$(RID)
 endif