Add missing gcc build dependency

libpng12.spec

@@ -1,7 +1,7 @@
 Summary: Old version of libpng, needed to run old binaries
 Name: libpng12
 Version: 1.2.57
-Release: 5%{?dist}
+Release: 6%{?dist}
 License: zlib
 URL: http://www.libpng.org/pub/png/
 
@@ -15,6 +15,7 @@ Source0: https://ftp-osl.osuosl.org/pub/libpng/src/libpng12/libpng-%{version}.ta
 Patch0: libpng12-multilib.patch
 Patch1: libpng12-pngconf.patch
 
+BuildRequires: gcc
 BuildRequires: pkgconfig
 BuildRequires: zlib-devel
 
@@ -82,6 +83,9 @@ make check
 %{_libdir}/pkgconfig/libpng12.pc
 
 %changelog
+* Tue Feb 20 2018 Nikola Forró <nforro@redhat.com> - 1.2.57-6
+- Add missing gcc build dependency
+
 * Wed Feb 07 2018 Fedora Release Engineering <releng@fedoraproject.org> - 1.2.57-5
 - Rebuilt for https://fedoraproject.org/wiki/Fedora_28_Mass_Rebuild