ld: Disable DT_RELR in some -z relro tests
Disable DT_RELR in the following -z relro tests which don't expect
DT_RELR in linker outputs.
* testsuite/ld-i386/pr20830.d: Pass $NO_DT_RELR_LDFLAGS to ld.
* testsuite/ld-x86-64/pr20830a-now.d: Likewise.
* testsuite/ld-x86-64/pr20830a.d: Likewise.
* testsuite/ld-x86-64/pr20830b-now.d: Likewise.
* testsuite/ld-x86-64/pr20830b.d: Likewise.
* testsuite/ld-x86-64/pr21038a-now.d: Likewise.
* testsuite/ld-x86-64/pr21038a.d: Likewise.
* testsuite/ld-x86-64/pr21038b-now.d: Likewise.
* testsuite/ld-x86-64/pr21038c-now.d: Likewise.
* testsuite/ld-x86-64/pr21038c.d: Likewise.