https://bugs.gentoo.org/870679

Generated file and configure.in is written for autoconf 2.13.
--- a/configure
+++ b/configure
@@ -751,7 +751,7 @@ cat > conftest.$ac_ext << EOF
 #line 752 "configure"
 #include "confdefs.h"
 
-main(){return(0);}
+int main(){return(0);}
 EOF
 if { (eval echo configure:757: \"$ac_link\") 1>&5; (eval $ac_link) 2>&5; } && test -s conftest${ac_exeext}; then
   ac_cv_prog_cc_works=yes