Add 2 more tests for PR ld/21884
    
    	PR ld/21884
    	* testsuite/ld-i386/i386.exp: Run pr21884.
    	* testsuite/ld-x86-64/x86-64.exp: Likewise.
    	* testsuite/ld-i386/pr21884.d: New file.
    	* testsuite/ld-i386/pr21884.t: Likewise.
    	* testsuite/ld-x86-64/pr21884.d: Likewise.
    	* testsuite/ld-x86-64/pr21884.t: Likewise.