[lldb] Add llgs_test decorator back to TestAutoInstallMainExecutable

This got removed in 68bb51acd572735d80d20adb2c2fc51a5cbbd88e and this enabled
the test on macOS (where it just causes lldb-server to crash). Re-adding the
decorator to get the tests passing again.

GitOrigin-RevId: c68a645acb833109f4bb0d859686b05a81b2be7d
1 file changed