testsuite supports_dt_relr

testsuite supports_dt_relr

Tidy, and fix "FAIL: Build dt-relr-glibc-1b.so" on all non-x86
linux targets.

binutils/
	* binutils-common.exp (supports_dt_relr): New proc.
ld/
	* testsuite/config/default.exp (DT_RELR_LDFLAGS, NO_DT_RELR_LDFLAGS),
	(DT_RELR_CC_LDFLAGS, NO_DT_RELR_CC_LDFLAGS): Use supports_dt_relr.
	* testsuite/ld-elf/dt-relr.exp: Don't run unless supports_dt_relr.
	* testsuite/ld-elf/dt-relr-1a.d: Likewise.
	* testsuite/ld-elf/dt-relr-1b.d: Likewise.
	* testsuite/ld-elf/dt-relr-1c.d: Likewise.
	* testsuite/ld-elf/dt-relr-2a.d: Likewise.
	* testsuite/ld-elf/dt-relr-2b.d: Likewise.
	* testsuite/ld-elf/dt-relr-2c.d: Likewise.
	* testsuite/ld-elf/dt-relr-2d.d: Likewise.
	* testsuite/ld-elf/dt-relr-2e.d: Likewise.
	* testsuite/ld-elf/dt-relr-2f.d: Likewise.
	* testsuite/ld-elf/dt-relr-2g.d: Likewise.
	* testsuite/ld-elf/dt-relr-2h.d: Likewise.
	* testsuite/ld-elf/dt-relr-3a.d: Likewise.
	* testsuite/ld-elf/dt-relr-3b.d: Likewise.