gnustep-make: detect TARGET_OS=linux-musl as linux target

It previously looked for the `gnu` part of TARGET_OS=linux-gnu

srcpkgs/gnustep-make/patches/musl.patch

@@ -0,0 +1,11 @@
+--- target.make.orig
++++ target.make
+@@ -553,7 +553,7 @@
+ # The following ifeq matches both 'linux-gnu' (which is GNU/Linux ELF)
+ # and 'gnu0.3' (I've been told GNUSTEP_TARGET_OS is 'gnu0.3' on
+ # GNU/Hurd at the moment).  We want the same code in both cases.
+-ifeq ($(findstring gnu, $(GNUSTEP_TARGET_OS)), gnu)
++ifeq ($(findstring linux, $(GNUSTEP_TARGET_OS)), linux)
+ HAVE_SHARED_LIBS        = yes
+ SHARED_LIB_LINK_CMD     = \
+         $(LD) $(SHARED_LD_PREFLAGS) -shared -Wl,-soname,$(LIB_LINK_SONAME_FILE) \

srcpkgs/gnustep-make/template

@@ -1,7 +1,7 @@
 # Template build file for 'gnustep-make'
 pkgname=gnustep-make
 version=2.7.0
-revision=2
+revision=3
 build_style=gnu-configure
 conf_files="/etc/GNUstep/GNUstep.conf"
 short_desc="GNU Step Makefile helpers for a GNUstep-based project"