Skip C++20 test if missing clang-scan-deps (#880)

The default `apt install clang` on ubuntu doesn't install
clang-scan-deps so this test failed.

Closes #880

COPYBARA_INTEGRATE_REVIEW=https://github.com/bazelbuild/rules_cc/pull/880 from keith:ks/skip-c-20-test-if-missing-clang-scan-deps d1cfb2fc7f113dc109edd70bd7b7eb5cc4ee6f58
PiperOrigin-RevId: 981300353
Change-Id: Iae7234c1de48fd6226e62bd7af807fddc68e08c2

tests/integration/cc_integration_test.sh

diff --git a/tests/integration/cc_integration_test.sh b/tests/integration/cc_integration_test.sh
index 98eda9d..0945605 100755
--- a/tests/integration/cc_integration_test.sh
+++ b/tests/integration/cc_integration_test.sh
@@ -2327,6 +2327,7 @@
 
 function test_cpp20_modules_with_clang() {
   type -P clang || return 0
+  type -P clang-scan-deps || return 0
   # Check if clang version is less than 17
   clang_version=$(clang --version | head -n1 | grep -oE '[0-9]+\.[0-9]+' | head -n1)
   if [[ -n "$clang_version" ]]; then