fix zstd compile error (#20918)
fix zstd compile error (#20918)

When compile envoy on RedHat based OS like Fedra, zstd will compile error with complaining: external/envoy/bazel/foreign_cc/BUILD:551:12: output 'external/envoy/bazel/foreign_cc/zstd/lib/libzstd.a' was not created
This is because on RedHat based OS, CMAKE_INSTALL_LIBDIR default is set to lib64, so it will generate object in external/envoy/bazel/foreign_cc/zstd/lib64/libzstd.a

Add the cmake compile flag `CMAKE_INSTALL_LIBDIR: lib` to fix this.

Signed-off-by: Felix Du <01529bfc062be2f2c5e28ee99979f3e170bfa4d6@gmail.com>

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