Compile prefix.c and osx.c only when needed to avoid warnings

When mac integration or binary relocation are disabled, the compiled
object file contains no symbols because the guards in the source files
hide all code. On OS X there's a warning during compilation saying:

/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ranlib:
file: .libs/libgeany.a(libgeany_la-prefix.o) has no symbols

If these features are disabled, don't compile the corresponding
sources to avoid the warnings.

Interestingly, waf compilation works without warnings - it appears
linking is done through g++ which doesn't produce these warnings.

m4/geany-binreloc.m4

@@ -52,9 +52,11 @@ AC_DEFUN([GEANY_CHECK_BINRELOC],
 		AC_MSG_RESULT([no (unknown value "$enable_binreloc")])
 		enable_binreloc=no
 	fi
-	if test "$enable_binreloc" = "yes"; then
+	AM_CONDITIONAL(ENABLE_BINRELOC, [test "$enable_binreloc" = "yes"])
+	AM_COND_IF(ENABLE_BINRELOC,
+	[
 		AC_DEFINE([ENABLE_BINRELOC],,[Use AutoPackage?])
-	fi
+	])
 
 	GEANY_STATUS_ADD([Enable binary relocation], [$enable_binreloc])
 ])

m4/geany-mac-integration.m4

@@ -9,7 +9,8 @@ AC_DEFUN([GEANY_CHECK_MAC_INTEGRATION],
 			[geany_enable_mac_integration="$enableval"],
 			[geany_enable_mac_integration="no"])
 
-	AS_IF([test "x$geany_enable_mac_integration" = "xyes"],
+	AM_CONDITIONAL(ENABLE_MAC_INTEGRATION, [test "x$geany_enable_mac_integration" = "xyes"])
+	AM_COND_IF(ENABLE_MAC_INTEGRATION,
 	[
 		AS_IF([test "x$enable_gtk3" = xyes],
 			[PKG_CHECK_MODULES(MAC_INTEGRATION, gtk-mac-integration-gtk3)], 

src/Makefile.am

@@ -81,10 +81,8 @@ libgeany_la_SOURCES = \
 	msgwindow.c msgwindow.h \
 	navqueue.c navqueue.h \
 	notebook.c notebook.h \
-	osx.c osx.h \
 	plugins.c plugins.h \
 	pluginutils.c pluginutils.h \
-	prefix.c prefix.h \
 	prefs.c prefs.h \
 	printing.c printing.h \
 	project.c project.h \
@@ -101,6 +99,14 @@ libgeany_la_SOURCES = \
 	ui_utils.c ui_utils.h \
 	utils.c utils.h
 
+if ENABLE_BINRELOC
+libgeany_la_SOURCES += prefix.c prefix.h
+endif
+
+if ENABLE_MAC_INTEGRATION
+libgeany_la_SOURCES += osx.c osx.h
+endif
+
 libgeany_la_CFLAGS  = $(AM_CPPFLAGS) @LIBGEANY_CFLAGS@
 libgeany_la_LDFLAGS = @LIBGEANY_LDFLAGS@