test(vulnfeeds): make flaky tests skippable on Cloud Build (#3154)

`cves.TestExtractGitCommit` and `cves.ValidateAndCanonicalizeLink` are
consistently failing on Cloud Build for git.kernel.org, which makes me
believe Cloud Build's egress IPs may have been blocked.

Rather than remove these tests entirely, this makes them skippable on
Cloud Build, and skips them, to unblock PRs that are currently
unmergeable due to these test failures.

cloudbuild.yaml

@@ -84,6 +84,8 @@ steps:
   id: 'vulnfeed-tests'
   dir: vulnfeeds
   args: ['bash', '-ex', 'run_tests.sh']
+  env:
+    - 'BUILD_ID=$BUILD_ID'
   waitFor: ['init']
 
 - name: 'gcr.io/oss-vdb/ci'

vulnfeeds/cves/versions_test.go

@@ -466,6 +466,7 @@ func TestExtractGitCommit(t *testing.T) {
 		inputCommitType        CommitType
 		expectedAffectedCommit AffectedCommit
 		expectFailure          bool
+		skipOnCloudBuild       bool
 	}{
 		{
 			description:     "Valid GitHub commit URL",
@@ -590,6 +591,7 @@ func TestExtractGitCommit(t *testing.T) {
 				Repo:  "https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git",
 				Fixed: "ee1fee900537b5d9560e9f937402de5ddc8412f3",
 			},
+			skipOnCloudBuild: true, // observing indications of IP denylisting as at 2025-02-13
 		},
 		{
 			description:     "Valid GitWeb commit URL",
@@ -628,6 +630,9 @@ func TestExtractGitCommit(t *testing.T) {
 	}
 
 	for _, tc := range tests {
+		if _, ok := os.LookupEnv("BUILD_ID"); ok && tc.skipOnCloudBuild {
+			t.Skipf("test %q: running on Cloud Build", tc.description)
+		}
 		got, err := extractGitCommit(tc.inputLink, tc.inputCommitType)
 		if err != nil && !tc.expectFailure {
 			t.Errorf("test %q: extractGitCommit for %q (%q) errored unexpectedly: %#v", tc.description, tc.inputLink, tc.inputCommitType, err)
@@ -1062,6 +1067,7 @@ func TestValidateAndCanonicalizeLink(t *testing.T) {
 		args              args
 		wantCanonicalLink string
 		wantErr           bool
+		skipOnCloudBuild  bool
 	}{
 		{
 			name: "A link that 404's",
@@ -1078,10 +1084,14 @@ func TestValidateAndCanonicalizeLink(t *testing.T) {
 			},
 			wantCanonicalLink: "https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ee1fee900537b5d9560e9f937402de5ddc8412f3",
 			wantErr:           false,
+			skipOnCloudBuild:  true, // observing indications of IP denylisting as at 2025-02-13
 		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
+			if _, ok := os.LookupEnv("BUILD_ID"); ok && tt.skipOnCloudBuild {
+				t.Skipf("test %q: running on Cloud Build", tt.name)
+			}
 			gotCanonicalLink, err := ValidateAndCanonicalizeLink(tt.args.link)
 			if (err != nil) != tt.wantErr {
 				t.Errorf("ValidateAndCanonicalizeLink() error = %v, wantErr %v", err, tt.wantErr)
@@ -1109,7 +1119,7 @@ func TestCommit(t *testing.T) {
 			args: args{
 				u: "https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ee1fee900537b5d9560e9f937402de5ddc8412f3",
 			},
-			want: "ee1fee900537b5d9560e9f937402de5ddc8412f3",
+			want:    "ee1fee900537b5d9560e9f937402de5ddc8412f3",
 			wantErr: false,
 		},
 	}
@@ -1125,4 +1135,4 @@ func TestCommit(t *testing.T) {
 			}
 		})
 	}
-}
+}