ci: Increase CCACHE_SIZE in some builds on Travis

ci/test/00_setup_env_native_msan.sh

@@ -20,3 +20,4 @@ export GOAL="install"
 export BITCOIN_CONFIG="--enable-wallet --with-sanitizers=memory --with-asm=no --prefix=${BASE_ROOT_DIR}/depends/x86_64-pc-linux-gnu/ CC=clang CXX=clang++ CFLAGS='${MSAN_FLAGS}' CXXFLAGS='${MSAN_AND_LIBCXX_FLAGS}' BDB_LIBS='-L${BDB_PREFIX}/lib -ldb_cxx-4.8' BDB_CFLAGS='-I${BDB_PREFIX}/include'"
 export USE_MEMORY_SANITIZER="true"
 export RUN_FUNCTIONAL_TESTS="false"
+export CCACHE_SIZE=250M