testsuite: require C compiler explicitly in tests needing it

testsuite: require C compiler explicitly in tests needing it

The list of the test scripts which needed a C compiler but
failed to require it explicitly has been found by running:
  $ am_explicit_skips=yes CC=false make check
and looking for tests that reported FAIL instead of SKIP.
After the present change, all those previously failing tests
either pass or get correctly skipped.

* tests/aclocal4.test ($required): Add `cc'.
* tests/ansi.test: Likewise.
* tests/ansi10.test: Likewise.
* tests/ansi3.test: Likewise.
* tests/ansi3b.test: Likewise.
* tests/ansi5.test: Likewise.
* tests/ansi6.test: Likewise.
* tests/ansi7.test: Likewise.
* tests/ansi9.test: Likewise.
* tests/backcompat6.test: Likewise.
* tests/canon7.test: Likewise.
* tests/check5.test: Likewise.
* tests/check7.test: Likewise.
* tests/check8.test: Likewise.
* tests/cond4.test: Likewise.
* tests/cond11.test: Likewise.
* tests/cond16.test: Likewise.
* tests/cond18.test: Likewise.
* tests/cond19.test: Likewise.
* tests/cond22.test: Likewise.
* tests/cond30.test: Likewise.
* tests/cond31.test: Likewise.
* tests/cond32.test: Likewise.
* tests/cond34.test: Likewise.
* tests/cond35.test: Likewise.
* tests/cond39.test: Likewise.
* tests/condd.test: Likewise.
* tests/cygnus-dependency-tracking.test: Likewise.
* tests/depcomp2.test: Likewise.
* tests/depcomp6.test: Likewise.
* tests/depcomp7.test: Likewise.
* tests/depcomp8a.test: Likewise.
* tests/depcomp8b.test: Likewise.
* tests/depdist.test: Likewise.
* tests/depend2.test: Likewise.
* tests/depend5.test: Likewise.
* tests/distcleancheck.test: Likewise.
* tests/distname.test: Likewise.
* tests/exeext.test: Likewise.
* tests/exeext4.test: Likewise.
* tests/extradep.test: Likewise.
* tests/extradep2.test: Likewise.
* tests/gnits2.test: Likewise.
* tests/gnits3.test: Likewise.
* tests/instdir-ltlib.test: Likewise.
* tests/instdir-prog.test: Likewise.
* tests/instfail.test: Likewise.
* tests/instfail-libtool.test: Likewise.
* tests/lex3.test: Likewise.
* tests/lex5.test: Likewise.
* tests/lexvpath.test: Likewise.
* tests/lex-subobj-nodep.test: Likewise.
* tests/lflags.test: Likewise.
* tests/libobj-basic.test: Likewise.
* tests/libobj2.test: Likewise.
* tests/libobj7.test: Likewise.
* tests/libobj10.test: Likewise.
* tests/libobj16a.test: Likewise.
* tests/libobj16b.test: Likewise.
* tests/libobj17.test: Likewise.
* tests/libobj19.test: Likewise.
* tests/libtool2.test: Likewise.
* tests/libtool3.test: Likewise.
* tests/libtool7.test: Likewise.
* tests/libtool9.test: Likewise.
* tests/libtoo10.test: Likewise.
* tests/libtoo11.test: Likewise.
* tests/ltcond.test: Likewise.
* tests/ltcond2.test: Likewise.
* tests/ltconv.test: Likewise.
* tests/ltinit.test: Likewise.
* tests/ltlibsrc.test: Likewise.
* tests/ltorder.test: Likewise.
* tests/nobase.test: Likewise.
* tests/nobase-libtool.test: Likewise.
* tests/mmodely.test: Likewise.
* tests/parallel-tests5.test: Likewise.
* tests/parallel-tests-suffix-prog.test: Likewise.
* tests/parallel-tests-ext-driver-prog.test: Likewise.
* tests/posixsubst-ldadd.test: Likewise.
* tests/posixsubst-libraries.test: Likewise.
* tests/posixsubst-ltlibraries.test: Likewise.
* tests/posixsubst-programs.test: Likewise.
* tests/posixsubst-sources.test: Likewise.
* tests/pr87.test: Likewise.
* tests/pr204.test: Likewise.
* tests/pr224.test: Likewise.
* tests/pr300-lib.test: Likewise.
* tests/pr300-ltlib.test: Likewise.
* tests/pr300-prog.test: Likewise.
* tests/pr401.test: Likewise.
* tests/pr401b.test: Likewise.
* tests/pr401c.test: Likewise.
* tests/remake-gnulib-add-acsubst.test: Likewise.
* tests/remake-gnulib-add-header.test: Likewise.
* tests/regex.test: Likewise.
* tests/repeated-options.test: Likewise.
* tests/silent.test: Likewise.
* tests/silent3.test: Likewise.
* tests/silent9.test: Likewise.
* tests/silent-lex-generic.test: Likewise.
* tests/silent-many-generic.test: Likewise.
* tests/silent-yacc-generic.test: Likewise.
* tests/specflg7.test: Likewise.
* tests/specflg9.test: Likewise.
* tests/specflg10.test: Likewise.
* tests/stdinc.test: Likewise.
* tests/strip.test: Likewise.
* tests/strip2.test: Likewise.
* tests/strip3.test: Likewise.
* tests/subdirbuiltsources.test: Likewise.
* tests/subobj3.test: Likewise.
* tests/subobj6.test: Likewise.
* tests/subobj11a.test: Likewise.
* tests/subpkg.test: Likewise.
* tests/subst2.test: Likewise.
* tests/subst3.test: Likewise.
* tests/substref.test: Likewise.
* tests/substre2.test: Likewise.
* tests/suffix5.test: Likewise.
* tests/suffix8.test: Likewise.
* tests/suffix10.test: Likewise.
* tests/suffix11.test: Likewise.
* tests/suffix12.test: Likewise.
* tests/suffix13.test: Likewise.
* tests/target-cflags.test: Likewise.
* tests/transform.test: Likewise.
* tests/transform2.test: Likewise.
* tests/yacc-basic.test: Likewise.
* tests/yacc-d-basic.test: Likewise.
* tests/yacc-clean.test: Likewise.
* tests/yacc-dist-nobuild.test: Likewise.
* tests/yacc-nodist.test: Likewise.
* tests/yaccvpath.test: Likewise.
* tests/yacc-d-vpath.test: Likewise.
* tests/yacc4.test: Likewise.
* tests/yacc7.test: Likewise.
* tests/yacc8.test: Likewise.
* tests/yaccdry.test: Likewise.
* tests/yflags-cmdline-override.test: Likewise.
* tests/yflags-force-override.test: Likewise.
* tests/python-virtualenv.test: Likewise.  Also, improve skip
messages.
* tests/subobj5.test ($required): Add `cc'.
(Makefile.am): Set `AUTOMAKE_OPTIONS' to `subdir-objects', and
add new checking rules `test-build' and `test-distdir'.
Extend the test by building and examining the distdir, the
program, and the object files.
* tests/postproc.test ($required): Add `cc'.
Avoid the explicit `|| Exit $?' after call to configure, which
is now either redundant (e.g., when `am_explicit_skips' is
unset), or counter-productive (e.g., when `am_explicit_skips'
is set to "yes").
* tests/pr243.test: Likewise.
* tests/pr266.test: Likewise.
* tests/pr220.test: Simplify so that it doesn't require a
C compiler anymore.
* tests/subdir5.test: Likewise.
* tests/subdir8.test: Likewise.
* tests/lflags.test: Likewise.
* tests/yflags.test: Likewise.
* tests/yflags-force-conditional.test: Likewise.
* tests/lflags2.test: Simplify so that it doesn't require a
C++ compiler anymore.
* tests/yflags2.test: Likewise.
* tests/autohdrdry.test (configure.in): Remove unneeded call
to `AC_PROG_CC'.
* tests/pr287.test: Likewise.
* tests/check6.test: Likewise.
* tests/cond21.test: Likewise, plus some cosmetic adjustments.
* tests/upc.test: Skip if configure fails with status `77'.
* tests/upc3.test: Likewise.
* tests/vala4.test: Likewise.
* tests/nostdinc.test: Likewise.  Also, make grepping checks
on `Makefile.in'.  Update heading comments.
* tests/compile5.test: When we must skip, skip explicitly,
and with a meaningful message.
* tests/instspc-tests.sh: When running in "test-build" or
"test-install" mode (as determined by the value of variable
`$instspc_action'), require `cc'.  Adjust comments.
* tests/depmod-tests.sh: Likewise.