libctf, testsuite: fix various warnings in tests

These warnings are all off by default, but if they do fire you get
spurious ERRORs when running make check-libctf.

libctf/ChangeLog
2021-09-27  Nick Alcock  <nick.alcock@oracle.com>

	* testsuite/libctf-lookup/enum-symbol.c: Remove unused label.
	* testsuite/libctf-lookup/conflicting-type-syms.c: Remove unused
	variables.
	* testsuite/libctf-regression/pptrtab.c: Likewise.
	* testsuite/libctf-regression/type-add-unnamed-struct.c: Likewise.
	* testsuite/libctf-writable/pptrtab.c: Likewise.
	* testsuite/libctf-writable/reserialize-strtab-corruption.c:
	Likewise.
	* testsuite/libctf-regression/nonstatic-var-section-ld-r.c: Fix
	format string.
	* testsuite/libctf-regression/nonstatic-var-section-ld.c:
	Likewise.
	* testsuite/libctf-regression/nonstatic-var-section-ld.lk: Adjust.
	* testsuite/libctf-writable/symtypetab-nonlinker-writeout.c: Fix
	initializer.