Add configure option to stop examples being built, --disable-examples.

- Added new configure option --disable-examples which can be used to
  stop the example programs being built. This can be useful in some
  situations, such as when cross compiling static libraries.

- Examples are still built by default, --disable-examples must be passed
  explicitly to stop them being built.

Signed-off-by: Ralph Giles <giles@thaumas.net>

Makefile.am

@@ -21,7 +21,9 @@ libopusurl_la_LIBADD = libopusfile.la $(URL_DEPS_LIBS)
 libopusurl_la_LDFLAGS = -no-undefined \
  -version-info @OP_LT_CURRENT@:@OP_LT_REVISION@:@OP_LT_AGE@
 
+if OP_ENABLE_EXAMPLES
 noinst_PROGRAMS = examples/opusfile_example examples/seeking_example
+endif
 
 examples_opusfile_example_SOURCES = examples/opusfile_example.c
 examples_seeking_example_SOURCES = examples/seeking_example.c

configure.ac

@@ -124,6 +124,11 @@ AS_IF([test "$enable_fixed_point" = "yes"],
   ]
 )
 
+AC_ARG_ENABLE([examples],
+  AS_HELP_STRING([--disable-examples], [Disable building of examples]),,
+  enable_examples=yes)
+AM_CONDITIONAL([OP_ENABLE_EXAMPLES], [test "$enable_examples" = "yes"])
+
 AS_CASE(["$ac_cv_search_lrintf"],
   ["no"],[],
   ["none required"],[],
@@ -172,6 +177,7 @@ AC_MSG_NOTICE([
 
     Hidden visibility ............ ${cc_cv_flag_visibility}
 
+    Building Examples ............ ${enable_examples}
     API documentation ............ ${enable_doc}
 ------------------------------------------------------------------------
 ])