libgc: Build specified prerelase snapshot

Build a specific prerelease version of libgc instead of building
from latest version automatically.

packages/libgc/build.sh

@@ -1,10 +1,11 @@
 TERMUX_PKG_HOMEPAGE=http://www.hboehm.info/gc/
 TERMUX_PKG_DESCRIPTION="Library providing the Boehm-Demers-Weiser conservative garbage collector"
-# The latest release 7.4.2 is too old for aarch64, use a master snapshot until 7.5:
-TERMUX_PKG_VERSION=7.4.`date "+%Y%m%d%H%M"`
-TERMUX_PKG_SRCURL=https://github.com/ivmai/bdwgc/archive/master.zip
+# The latest release 7.4.2 is too old for aarch64, use the version
+# https://github.com/ivmai/bdwgc/tree/c861ec3d1825b5bb450d20bf9091562fa8a81a4d
+# from 2016-0-114 21:34 for now.
+TERMUX_PKG_VERSION=7.4.201601142134
+TERMUX_PKG_SRCURL=https://github.com/ivmai/bdwgc/archive/c861ec3d1825b5bb450d20bf9091562fa8a81a4d.zip
 TERMUX_PKG_FOLDERNAME=bdwgc-master
-TERMUX_PKG_NO_SRC_CACHE=yes
 TERMUX_PKG_RM_AFTER_INSTALL="share/gc"
 
 # Avoid defining structs already defined in api level 21 or beyond