ci: cleanup C*FLAG usage in Valgrind jobs

This was being used to avoid a missing -O2. After the previous commits,
this is no-longer an issue.

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 using Valgrind 3.20 or later
-export BITCOIN_CONFIG="--enable-fuzz --with-sanitizers=fuzzer CC='clang -gdwarf-4' CXX='clang++ -gdwarf-4'"
+export BITCOIN_CONFIG="--enable-fuzz --with-sanitizers=fuzzer CC=clang CXX=clang++ CFLAGS=-gdwarf-4 CXXFLAGS=-gdwarf-4"
 export CCACHE_MAXSIZE=200M

ci/test/00_setup_env_native_valgrind.sh

@@ -14,4 +14,4 @@ export NO_DEPENDS=1
 export TEST_RUNNER_EXTRA="--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 using Valgrind 3.20 or later
-export BITCOIN_CONFIG="--enable-zmq --with-incompatible-bdb --with-gui=no CC='clang -gdwarf-4' CXX='clang++ -gdwarf-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