[PATCH] configure: Improve failures due to missing pkg-config

[Ismael Luceno]

Output a warning at the beginning, and fill PKG_CONFIG with "false" so
that any auto-configuration attempts fail without bogus messages.

Signed-off-by: Ismael Luceno <ismael at iodev.co.uk>
---
 configure.ac | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/configure.ac b/configure.ac
index 1f119c5baeeb..29d043f18950 100644
--- a/configure.ac
+++ b/configure.ac
@@ -19,6 +19,9 @@ AC_PROG_MKDIR_P
 AC_PROG_LN_S
 AC_PROG_SED
 PKG_PROG_PKG_CONFIG
+AS_IF([test -z "$PKG_CONFIG"],
+  [AC_MSG_WARN([pkg-config is needed for auto-configuration of dependencies])
+   PKG_CONFIG=false])
 AM_PATH_ALSA(1.0.27)
 if test "x$enable_alsatest" = "xyes"; then
 AC_CHECK_FUNC([snd_ctl_elem_add_enumerated],
-- 
2.28.0