require gcc for building

pngcrush.spec

@@ -11,7 +11,11 @@ URL:            http://pmt.sourceforge.net/%{name}/
 Source0:        http://downloads.sourceforge.net/pmt/%{name}-%{version}-nolib.tar.xz
 # from Debian sid.
 Source1:        %{name}.sgml
-BuildRequires:  libpng-devel, zlib-devel, pkgconfig, docbook-utils
+BuildRequires:  docbook-utils
+BuildRequires:  gcc
+BuildRequires:  libpng-devel
+BuildRequires:  pkgconfig
+BuildRequires:  zlib-devel
 
 %description
 pngcrush is a commandline optimizer for PNG (Portable Network Graphics) files.
@@ -45,6 +49,7 @@ docbook2man %{name}.sgml
 - version 1.8.13
 - ship license
 - remove some old packaging cruft
+- require gcc for building
 
 * Fri Feb 09 2018 Fedora Release Engineering <releng@fedoraproject.org> - 1.8.11-2
 - Rebuilt for https://fedoraproject.org/wiki/Fedora_28_Mass_Rebuild