Expand handling of unconverted deps in bp2build

Support three options for converting modules with unconverted
dependencies
1. (default) Warn when converting a module if it has unconverted deps.
2. Error when encountering a module with unconverted deps. (not hooked
up yet)

Test: build/bazel/ci/bp2build.sh
Test: build/bazel/ci/mixed_libc.sh
Test: BP2BUILD_ERROR_UNCONVERTED=1 build/bazel/ci/bp2build.sh with
      unconverted deps -- get appropriate error
Bug: 181155349
Change-Id: Ifaabf0cd2e43e963366dc137159c705294165c3d
diff --git a/bp2build/genrule_conversion_test.go b/bp2build/genrule_conversion_test.go
index a991180..f3bc1ba 100644
--- a/bp2build/genrule_conversion_test.go
+++ b/bp2build/genrule_conversion_test.go
@@ -267,7 +267,8 @@
 		}
 
 		codegenCtx := NewCodegenContext(config, *ctx.Context, Bp2Build)
-		bazelTargets := generateBazelTargetsForDir(codegenCtx, checkDir)
+		bazelTargets, err := generateBazelTargetsForDir(codegenCtx, checkDir)
+		android.FailIfErrored(t, err)
 		if actualCount, expectedCount := len(bazelTargets), len(testCase.expectedBazelTargets); actualCount != expectedCount {
 			t.Errorf("%s: Expected %d bazel target, got %d", testCase.description, expectedCount, actualCount)
 		} else {
@@ -461,7 +462,8 @@
 		android.FailIfErrored(t, errs)
 
 		codegenCtx := NewCodegenContext(config, *ctx.Context, Bp2Build)
-		bazelTargets := generateBazelTargetsForDir(codegenCtx, dir)
+		bazelTargets, err := generateBazelTargetsForDir(codegenCtx, dir)
+		android.FailIfErrored(t, err)
 		if actualCount := len(bazelTargets); actualCount != 1 {
 			t.Fatalf("%s: Expected 1 bazel target, got %d", testCase.description, actualCount)
 		}