Remove CFLAGS override from coverage build

Let Makefile handle coverage flags. The CFLAGS override was interfering
with the coverage build which needs specific compiler options.

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

Author: claude

.gitlab-ci.yml

@@ -192,7 +192,7 @@ coverage:generate:
     - apt-get install -y -qq build-essential clang llvm llvm-tools
   script:
     - make clean
-    - CFLAGS="-march=x86-64" make test-coverage
+    - make test-coverage
     - llvm-cov gcov -r build/*-coverage.gcno
     - mkdir -p coverage_report
     - find build -name "*.gcov" -exec cp {} coverage_report/ \;