ci: better pin to dwarf4 in valgrind job

Use `-gdwarf` and also set CFLAGS. I was seeing Valgrind issues otherwise.

ci/test/00_setup_env_native_fuzz_with_valgrind.sh

@@ -16,5 +16,5 @@ export RUN_FUZZ_TESTS=true
 export FUZZ_TESTS_CONFIG="--valgrind"
 export GOAL="install"
 # Temporarily pin dwarf 4, until valgrind can understand clang's dwarf 5
-export BITCOIN_CONFIG="--enable-fuzz --with-sanitizers=fuzzer CC=clang CXX=clang++ CXXFLAGS='-fdebug-default-version=4'"
+export BITCOIN_CONFIG="--enable-fuzz --with-sanitizers=fuzzer CC=clang CXX=clang++ CFLAGS='-gdwarf-4' CXXFLAGS='-gdwarf-4'"
 export CCACHE_SIZE=200M

ci/test/00_setup_env_native_valgrind.sh

@@ -14,4 +14,4 @@ export NO_DEPENDS=1
 export TEST_RUNNER_EXTRA="--nosandbox --exclude feature_init,rpc_bind,feature_bind_extra"  # Excluded for now, see https://github.com/bitcoin/bitcoin/issues/17765#issuecomment-602068547
 export GOAL="install"
 # Temporarily pin dwarf 4, until valgrind can understand clang's dwarf 5
-export BITCOIN_CONFIG="--enable-zmq --with-incompatible-bdb --with-gui=no CC=clang CXX=clang++ CXXFLAGS='-fdebug-default-version=4'"  # TODO enable GUI
+export BITCOIN_CONFIG="--enable-zmq --with-incompatible-bdb --with-gui=no CC=clang CXX=clang++ CFLAGS='-gdwarf-4' CXXFLAGS='-gdwarf-4'"  # TODO enable GUI