x86: Remove x86 ISA properties with empty bits
    
    There is no need to generate x86 ISA properties with empty bits in
    linker output.
    
    bfd/
    
    	PR ld/23372
    	* elfxx-x86.c (_bfd_x86_elf_merge_gnu_properties): Remove x86
    	ISA properties with empty bits.
    
    ld/
    
    	PR ld/23372
    	* testsuite/ld-i386/i386.exp: Run pr23372a and pr23372b.
    	* testsuite/ld-i386/pr23372a.d: New file.
    	* testsuite/ld-i386/pr23372a.s: Likewise.
    	* testsuite/ld-i386/pr23372b.d: Likewise.
    	* testsuite/ld-i386/pr23372b.s: Likewise.
    	* testsuite/ld-i386/pr23372c.s: Likewise.
    	* testsuite/ld-x86-64/pr23372a-x32.d: Likewise.
    	* testsuite/ld-x86-64/pr23372a.d: Likewise.
    	* testsuite/ld-x86-64/pr23372a.s: Likewise.
    	* testsuite/ld-x86-64/pr23372b-x32.d: Likewise.
    	* testsuite/ld-x86-64/pr23372b.d: Likewise.
    	* testsuite/ld-x86-64/pr23372b.s: Likewise.
    	* testsuite/ld-x86-64/pr23372c.s: Likewise.
    	* testsuite/ld-x86-64/x86-64.exp: Run pr23372a, pr23372a-x32,
    	pr23372b and pr23372b-x32.
    
    (cherry picked from commit 56ad703d56ffe5dc55d5e719a6ec41fd6cf9bfbe)