build: Pass CC to the test suite

If the build system does not have gcc available, the Dpkg::Arch module
requires the CC environment variable to be set so that we can detect
the host system.

check.am

@@ -29,6 +29,7 @@ check-local: $(test_data) $(test_programs) $(test_scripts)
 	  LC_ALL=C \
 	  $(TEST_ENV_VARS) \
 	  srcdir=$(srcdir) builddir=$(builddir) \
+	  CC=$(CC) \
 	  PERL_DL_NONLAZY=1 \
 	  PERL5OPT=$(TEST_COVERAGE) \
 	  $(PERL) -MTAP::Harness -e $(TEST_RUNNER) \

debian/changelog

@@ -109,6 +109,7 @@ dpkg (1.18.0) UNRELEASED; urgency=low
       build failure on uclibc based systems. Closes: #777044
       Based on a patch by Alex Potapenko <opotapenko@gmail.com>.
     - Use single suffix rules instead of non-portable %-pattern rules.
+    - Pass CC to the test suite, so that we can use a non-gcc compiler.
   * Packaging:
     - Remove old trigger related Breaks and Conflicts from dpkg.
     - Only use stackprotectorstrong when building dpkg with gcc >= 4.9.