libpam: Fix build with LLD linker

libpam: Fix build with LLD linker

LLD is strict about versioned symbols unlike BFD linker, it flags
undefined ones, Allow undefined symbols like BFD linker

Fixes
| riscv64-yoe-linux-ld.lld: error: version script assignment of 'global' to symbol 'pam_sm_acct_mgmt' failed: symbol not defined
| riscv64-yoe-linux-ld.lld: error: version script assignment of 'global' to symbol 'pam_sm_chauthtok' failed: symbol not defined
| riscv64-yoe-linux-ld.lld: error: version script assignment of 'global' to symbol 'pam_sm_close_session' failed: symbol not defined
| riscv64-yoe-linux-ld.lld: error: version script assignment of 'global' to symbol 'pam_sm_open_session' failed: symbol not defined
| riscv64-yoe-linux-clang: error: linker command failed with exit code 1 (use -v to see invocation)

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>