x11-themes/gtk-engines-rezlooks: fix build with slibtool (link against -lm)

Closes: https://bugs.gentoo.org/782634
Signed-off-by: Sam James <sam@gentoo.org>

x11-themes/gtk-engines-rezlooks/files/gtk-engines-rezlooks-0.6-slibtool-sqrt-math.patch

@@ -0,0 +1,12 @@
+https://bugs.gentoo.org/782634
+--- a/configure.ac
++++ b/configure.ac
+@@ -21,6 +21,8 @@ disableval="y"
+ 
+ AC_ARG_ENABLE(animation, 	[  --enable-animation		compile rezlooks with animation support], 	[animation=$disableval], 	[animation=$enableval])
+ 
++AC_SEARCH_LIBS([sqrt], [m])
++
+ PKG_CHECK_MODULES(GTK, gtk+-2.0 >= 2.8.0,,
+                   AC_MSG_ERROR([GTK+-2.8 is required to compile rezlooks]))
+ 

x11-themes/gtk-engines-rezlooks/gtk-engines-rezlooks-0.6-r1.ebuild

@@ -1,4 +1,4 @@
-# Copyright 1999-2020 Gentoo Authors
+# Copyright 1999-2021 Gentoo Authors
 # Distributed under the terms of the GNU General Public License v2
 
 EAPI=7
@@ -19,7 +19,10 @@ BDEPEND="virtual/pkgconfig"
 
 S="${WORKDIR}"/rezlooks-${PV}
 
-PATCHES=( "${FILESDIR}"/${PN}-0.6-glib-single-include.patch )
+PATCHES=(
+	"${FILESDIR}"/${PN}-0.6-glib-single-include.patch
+	"${FILESDIR}"/${PN}-0.6-slibtool-sqrt-math.patch
+)
 
 src_prepare() {
 	default