coverage: improve llvm-cov detection

Signed-off-by: Jannik Glückert <jannik.glueckert@gmail.com>
(cherry picked from commit 6258f0d)

mesonbuild/environment.py

@@ -148,6 +148,9 @@ def find_coverage_tools(coredata: coredata.CoreData) -> T.Tuple[T.Optional[str],
     gcovr_exe, gcovr_version = detect_gcovr()
 
     llvm_cov_exe = detect_llvm_cov(compute_llvm_suffix(coredata))
+    # Some platforms may provide versioned clang but only non-versioned llvm utils
+    if llvm_cov_exe is None:
+        llvm_cov_exe = detect_llvm_cov('')
 
     lcov_exe, lcov_version, genhtml_exe = detect_lcov_genhtml()