configure.ac: try to fix addr2line build failure

https://rubyci.org/logs/rubyci.s3.amazonaws.com/debian8/ruby-trunk/log/20181228T063002Z.fail.html.gz
https://rubyci.org/logs/rubyci.s3.amazonaws.com/scw-9d6766/ruby-trunk/log/20181228T081706Z.fail.html.gz
https://rubyci.org/logs/rubyci.s3.amazonaws.com/gentoo/ruby-trunk/log/20181228T063002Z.fail.html.gz
https://rubyci.org/logs/rubyci.s3.amazonaws.com/centos6/ruby-trunk/log/20181228T063003Z.fail.html.gz
https://rubyci.org/logs/rubyci.s3.amazonaws.com/centos7/ruby-trunk/log/20181228T080003Z.fail.html.gz
https://rubyci.org/logs/rubyci.s3.amazonaws.com/opensuseleap/ruby-trunk/log/20181228T080002Z.fail.html.gz
https://rubyci.org/logs/rubyci.s3.amazonaws.com/rhel_zlinux/ruby-trunk/log/20181228T063303Z.fail.html.gz
https://rubyci.org/logs/rubyci.s3.amazonaws.com/icc-x64/ruby-trunk/log/20181228T090003Z.fail.html.gz

I suspect r66598 triggered something.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@66605 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

configure.ac

@@ -187,7 +187,7 @@ AS_IF([test x"${build}" != x"${host}"], [
   AC_CHECK_TOOL(CC, gcc)
 ])
 
-AC_PROG_CC
+AC_PROG_CC_C99
 AS_CASE([$CC],
 [gcc-*], [
     gcc_prefix=gcc- gcc_suffix=`echo "$CC" | sed 's/^gcc//'`