Only include the compat syscall stubs on Linux systems

These are Linux specific syscalls. Other systems either already have
these function on their libc, or would need different implementations.
This restores the previous behavior before the build system modernization.

Gbp-Pq: Name syscalls-linux.patch

configure.ac

@@ -24,6 +24,7 @@ AC_PREFIX_DEFAULT(/usr)
 AM_INIT_AUTOMAKE([-Wall foreign 1.11 dist-xz subdir-objects])
 AM_SILENT_RULES([yes])
 
+AC_CANONICAL_HOST
 AC_PROG_CC
 AM_PROG_CC_C_O
 AC_USE_SYSTEM_EXTENSIONS
@@ -49,6 +50,11 @@ dnl Automatically increment the revision for every release.
 LT_REVISION=$(echo "${PACKAGE_VERSION}" | tr -d .)
 AC_SUBST(LT_REVISION)
 
+AS_CASE([$host_os],
+	[linux*], [os_linux=yes],
+)
+AM_CONDITIONAL([OS_LINUX], [test "x$os_linux" = "xyes"])
+
 AC_CONFIG_COMMANDS([include/attr],
 	[dnl
 	rm -rf include/attr

libattr/Makemodule.am

@@ -8,19 +8,30 @@ LT_CURRENT = 2
 LT_AGE = 1
 LTVERSION = $(LT_CURRENT):$(LT_REVISION):$(LT_AGE)
 
-libattr_la_DEPENDENCIES = exports libattr/libattr.lds
+libattr_la_DEPENDENCIES = \
+	exports
+if OS_LINUX
+libattr_la_DEPENDENCIES += \
+	libattr/libattr.lds
+endif
 libattr_la_SOURCES = \
 	libattr/attr_copy_action.c \
 	libattr/attr_copy_check.c \
 	libattr/attr_copy_fd.c \
 	libattr/attr_copy_file.c \
 	libattr/libattr.c \
-	libattr/syscalls.c \
 	libattr/libattr.h
+if OS_LINUX
+libattr_la_SOURCES += \
+	libattr/syscalls.c
+endif
 libattr_la_CFLAGS = -include libattr/libattr.h
 libattr_la_LDFLAGS = \
 	-Wl,--version-script,$(top_srcdir)/exports \
-	-Wl,$(top_srcdir)/libattr/libattr.lds \
 	-version-info $(LTVERSION)
+if OS_LINUX
+libattr_la_LDFLAGS += \
+	-Wl,$(top_srcdir)/libattr/libattr.lds
+endif
 
 EXTRA_DIST += libattr/libattr.lds