Build: Prepare to support Automake's subdir-objects.

Due to a bug in Automake, subdir-objects won't be enabled
for now.

http://debbugs.gnu.org/cgi/bugreport.cgi?bug=17354

Thanks to Daniel Richard G. for the original patches.

configure.ac

diff --git a/configure.ac b/configure.ac
index e41979b..12c0117 100644
--- a/configure.ac
+++ b/configure.ac
@@ -482,7 +482,12 @@
 echo
 echo "Initializing Automake:"
 
-AM_INIT_AUTOMAKE([1.12 foreign tar-v7 filename-length-max=99 serial-tests])
+# We don't use "subdir-objects" yet because it breaks "make distclean" when
+# dependencies are enabled (as of Automake 1.14.1) due to this bug:
+# http://debbugs.gnu.org/cgi/bugreport.cgi?bug=17354
+# The -Wno-unsupported is used to silence warnings about missing
+# "subdir-objects".
+AM_INIT_AUTOMAKE([1.12 foreign tar-v7 filename-length-max=99 serial-tests -Wno-unsupported])
 AC_PROG_LN_S
 
 AC_PROG_CC_C99

src/Makefile.am

diff --git a/src/Makefile.am b/src/Makefile.am
index 9fb4caa..d199e85 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -19,4 +19,24 @@
 SUBDIRS += scripts
 endif
 
-EXTRA_DIST = common
+EXTRA_DIST = \
+	common/common_w32res.rc \
+	common/mythread.h \
+	common/sysdefs.h \
+	common/tuklib_common.h \
+	common/tuklib_config.h \
+	common/tuklib_cpucores.c \
+	common/tuklib_cpucores.h \
+	common/tuklib_exit.c \
+	common/tuklib_exit.h \
+	common/tuklib_gettext.h \
+	common/tuklib_integer.h \
+	common/tuklib_mbstr_fw.c \
+	common/tuklib_mbstr.h \
+	common/tuklib_mbstr_width.c \
+	common/tuklib_open_stdxxx.c \
+	common/tuklib_open_stdxxx.h \
+	common/tuklib_physmem.c \
+	common/tuklib_physmem.h \
+	common/tuklib_progname.c \
+	common/tuklib_progname.h

src/liblzma/Makefile.am

diff --git a/src/liblzma/Makefile.am b/src/liblzma/Makefile.am
index 1b40910..3720532 100644
--- a/src/liblzma/Makefile.am
+++ b/src/liblzma/Makefile.am
@@ -32,10 +32,10 @@
 	-Wl,--version-script=$(top_srcdir)/src/liblzma/liblzma.map
 endif
 
-liblzma_la_SOURCES += $(top_srcdir)/src/common/tuklib_physmem.c
+liblzma_la_SOURCES += ../common/tuklib_physmem.c
 
 if COND_THREADS
-liblzma_la_SOURCES += $(top_srcdir)/src/common/tuklib_cpucores.c
+liblzma_la_SOURCES += ../common/tuklib_cpucores.c
 endif
 
 include $(srcdir)/common/Makefile.inc

src/lzmainfo/Makefile.am

diff --git a/src/lzmainfo/Makefile.am b/src/lzmainfo/Makefile.am
index b90b3b3..ff7172b 100644
--- a/src/lzmainfo/Makefile.am
+++ b/src/lzmainfo/Makefile.am
@@ -9,8 +9,8 @@
 
 lzmainfo_SOURCES = \
 	lzmainfo.c \
-	$(top_srcdir)/src/common/tuklib_progname.c \
-	$(top_srcdir)/src/common/tuklib_exit.c
+	../common/tuklib_progname.c \
+	../common/tuklib_exit.c
 
 if COND_W32
 lzmainfo_SOURCES += lzmainfo_w32res.rc

src/xz/Makefile.am

diff --git a/src/xz/Makefile.am b/src/xz/Makefile.am
index 088319b..1f4a279 100644
--- a/src/xz/Makefile.am
+++ b/src/xz/Makefile.am
@@ -33,11 +33,11 @@
 	suffix.h \
 	util.c \
 	util.h \
-	$(top_srcdir)/src/common/tuklib_open_stdxxx.c \
-	$(top_srcdir)/src/common/tuklib_progname.c \
-	$(top_srcdir)/src/common/tuklib_exit.c \
-	$(top_srcdir)/src/common/tuklib_mbstr_width.c \
-	$(top_srcdir)/src/common/tuklib_mbstr_fw.c
+	../common/tuklib_open_stdxxx.c \
+	../common/tuklib_progname.c \
+	../common/tuklib_exit.c \
+	../common/tuklib_mbstr_width.c \
+	../common/tuklib_mbstr_fw.c
 
 if COND_W32
 xz_SOURCES += xz_w32res.rc

src/xzdec/Makefile.am

diff --git a/src/xzdec/Makefile.am b/src/xzdec/Makefile.am
index 70746c0..5ff8e37 100644
--- a/src/xzdec/Makefile.am
+++ b/src/xzdec/Makefile.am
@@ -14,8 +14,8 @@
 
 xzdec_SOURCES = \
 	xzdec.c \
-	$(top_srcdir)/src/common/tuklib_progname.c \
-	$(top_srcdir)/src/common/tuklib_exit.c
+	../common/tuklib_progname.c \
+	../common/tuklib_exit.c
 
 if COND_W32
 xzdec_SOURCES += xzdec_w32res.rc
@@ -37,8 +37,8 @@
 
 lzmadec_SOURCES = \
 	xzdec.c \
-	$(top_srcdir)/src/common/tuklib_progname.c \
-	$(top_srcdir)/src/common/tuklib_exit.c
+	../common/tuklib_progname.c \
+	../common/tuklib_exit.c
 
 if COND_W32
 lzmadec_SOURCES += lzmadec_w32res.rc