devel/libsigc++20: Update to 2.12.1

* Add GitHub mirror
* Update WWW entry
* Remove INSTALL_TARGET (unused)

Changelog:
https://github.com/libsigcplusplus/libsigcplusplus/releases/tag/2.12.1

PR:		280173
Approved by:	gnome (fluffy) via Matrix
Sponsored by:	Blinkinblox

devel/libsigc++20/Makefile

@@ -1,18 +1,18 @@
 PORTNAME=	libsigc++
-PORTVERSION=	2.12.0
+DISTVERSION=	2.12.1
 CATEGORIES=	devel
-MASTER_SITES=	GNOME
+MASTER_SITES=	GNOME \
+		https://github.com/libsigcplusplus/libsigcplusplus/releases/download/${DISTVERSION}/
 
 MAINTAINER=	gnome@FreeBSD.org
 COMMENT=	Callback Framework for C++
-WWW=		http://libsigc.sourceforge.net/
+WWW=		https://github.com/libsigcplusplus/libsigcplusplus
 
 LICENSE=	LGPL21+
 LICENSE_FILE=	${WRKSRC}/COPYING
 
 PORTSCOUT=	limit:^2\.12\.
 
-INSTALL_TARGET=	install-strip
 USES=		compiler:c++11-lang meson tar:xz
 USE_LDCONFIG=	yes
 

devel/libsigc++20/distinfo

@@ -1,3 +1,3 @@
-TIMESTAMP = 1685046103
-SHA256 (libsigc++-2.12.0.tar.xz) = 1c466d2e64b34f9b118976eb21b138c37ed124d0f61497df2a90ce6c3d9fa3b5
-SIZE (libsigc++-2.12.0.tar.xz) = 5002560
+TIMESTAMP = 1720347977
+SHA256 (libsigc++-2.12.1.tar.xz) = a9dbee323351d109b7aee074a9cb89ca3e7bcf8ad8edef1851f4cf359bd50843
+SIZE (libsigc++-2.12.1.tar.xz) = 5041732

devel/libsigc++20/files/patch-meson.build

@@ -0,0 +1,11 @@
+--- meson.build.orig	2024-08-06 18:25:19 UTC
++++ meson.build
+@@ -102,7 +102,7 @@ install_datadir = get_option('datadir')
+ install_includedir = get_option('includedir')
+ install_libdir = get_option('libdir')
+ install_datadir = get_option('datadir')
+-install_pkgconfigdir = install_libdir / 'pkgconfig'
++install_pkgconfigdir = install_prefix / 'libdata' / 'pkgconfig'
+ 
+ # Dependencies.
+ # sigcxx_build_dep: Dependencies when building the libsigc++ library.