Export RunBp2BuildTestCaseSimple() in testing.go

This is to support the migration of conversion tests to be next
to the files they're testing

Bug: 242070498
Test: m bp2build
Change-Id: I66243d420743273e7ebad70886cfe690740182c4
diff --git a/bp2build/linker_config_conversion_test.go b/bp2build/linker_config_conversion_test.go
index c4c4d87..5e7bcd4 100644
--- a/bp2build/linker_config_conversion_test.go
+++ b/bp2build/linker_config_conversion_test.go
@@ -25,7 +25,7 @@
 	t.Helper()
 	(&tc).ModuleTypeUnderTest = "linker_config"
 	(&tc).ModuleTypeUnderTestFactory = linkerconfig.LinkerConfigFactory
-	runBp2BuildTestCaseSimple(t, tc)
+	RunBp2BuildTestCaseSimple(t, tc)
 }
 
 func TestLinkerConfigConvertsSrc(t *testing.T) {