Rename test-suite test case to prevent NOEXE failures

In the test-suite, we have two files:
  SingleSource/UnitTests/Vector/Altivec/ld.reference_output
  SingleSource/UnitTests/Vector/Altivec/ld.c

That need to have their name changed to:
  SingleSource/UnitTests/Vector/Altivec/vec_ld.reference_output
  SingleSource/UnitTests/Vector/Altivec/vec_ld.c

Because they cause other test cases in the directory to not produce
executable once the ld test is built. The reason for the failure is that
the ./ld is used as the linker when building other tests.
diff --git a/SingleSource/UnitTests/Vector/Altivec/ld.c b/SingleSource/UnitTests/Vector/Altivec/vec_ld.c
similarity index 100%
rename from SingleSource/UnitTests/Vector/Altivec/ld.c
rename to SingleSource/UnitTests/Vector/Altivec/vec_ld.c
diff --git a/SingleSource/UnitTests/Vector/Altivec/ld.reference_output b/SingleSource/UnitTests/Vector/Altivec/vec_ld.reference_output
similarity index 100%
rename from SingleSource/UnitTests/Vector/Altivec/ld.reference_output
rename to SingleSource/UnitTests/Vector/Altivec/vec_ld.reference_output