[wip/mk/sysdep] Add a sysdep for liblzma

liblzma is the XZ-format compression library.

XZ is the successor to the Lempel-Ziv/Markov-chain Algorithm compression
format, which provides memory-hungry but powerful compression (often
better than bzip2) and fast, easy decompression.

The native format of liblzma is XZ; it also supports raw (headerless)
streams and the older LZMA format used by lzma.

mk/sysdep/liblzma.mk

+# robotpkg sysdep/liblzma.mk
+# Created:			Arnaud Degroote on Mar 29 2013
+
+DEPEND_DEPTH:=		${DEPEND_DEPTH}+
+LIBLZMA_DEPEND_MK:=		${LIBLZMA_DEPEND_MK}+
+
+ifeq (+,$(DEPEND_DEPTH))
+DEPEND_PKG+=		liblzma
+endif
+
+ifeq (+,$(LIBLZMA_DEPEND_MK)) # ------------------------------------------------
+
+PREFER.liblzma?=		system
+DEPEND_USE+=			liblzma
+DEPEND_ABI.liblzma?=	liblzma>=5.0
+
+SYSTEM_SEARCH.liblzma=	\
+	'include/lzma.h'	           \
+	'lib/liblzma.so'			  \
+	'lib/pkgconfig/liblzma.pc:/Version/s/[^.0-9]//gp'
+
+SYSTEM_PKG.Fedora.liblzma=	liblzma-devel
+SYSTEM_PKG.Ubuntu.liblzma=	liblzma-dev
+SYSTEM_PKG.Debian.liblzma=	liblzma-dev
+SYSTEM_PKG.NetBSD.liblzma=	archivers/xz
+
+endif # LIBLZMA_DEPEND_MK ------------------------------------------------------
+
+DEPEND_DEPTH:=		${DEPEND_DEPTH:+=}