Add a --{enable,disable}-progs configure option

Add a --{enable,disable}-progs configuration option to elfutils. This
allows to selectively disable the compilation of the elfutils programs
(in which case only the libraries are built and installed). This is
useful because the programs are often not needed, and also because
building the programs against uClibc causes several issues (lack of
obstack_printf() in uClibc for example).

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

Index: b/Makefile.am
===================================================================
--- a/Makefile.am
+++ b/Makefile.am
@@ -22,9 +22,13 @@
 
 pkginclude_HEADERS = version.h
 
+if ENABLE_PROGS
+PROGS_SUBDIR = src
+endif
+
 # Add doc back when we have some real content.
 SUBDIRS = config m4 lib libelf libebl libdwfl libdw libcpu libasm backends \
-	  src po tests
+	  $(PROGS_SUBDIR) po tests
 
 EXTRA_DIST = elfutils.spec GPG-KEY NOTES CONTRIBUTING \
 	     COPYING COPYING-GPLV2 COPYING-LGPLV3
Index: b/configure.ac
===================================================================
--- a/configure.ac
+++ b/configure.ac
@@ -263,6 +263,12 @@
 AC_DEFINE_UNQUOTED(LIBEBL_SUBDIR, "$LIBEBL_SUBDIR")
 AH_TEMPLATE([LIBEBL_SUBDIR], [$libdir subdirectory containing libebl modules.])
 
+AC_ARG_ENABLE([progs],
+	AS_HELP_STRING([--enable-progs], [enable progs]),
+	enable_progs=$enableval,
+	enable_progs=yes)
+AM_CONDITIONAL(ENABLE_PROGS, test "$enable_progs" = yes)
+
 dnl Test for zlib and bzlib, gives ZLIB/BZLIB .am
 dnl conditional and config.h USE_ZLIB/USE_BZLIB #define.
 save_LIBS="$LIBS"