That's less a limitation of the build system and more an intentional policy to ensure reproducible binaries etc.

Technically bazel can load any external files, but they must be tracked as workspace dependencies, which is more verbose:

E.g.

    new_local_repository(
        name = "system_libs",
        # pkg-config --variable=libdir x11
        path = "/usr/lib/x86_64-linux-gnu",
        build_file_content = """

cc_library( name = "x11", srcs = ["libX11.so"], visibility = ["//visibility:public"], ) """, )

That's a feature, no?