[PATCH] autotools.bbclass: Add functionality to force a distclean when reconfiguring

[Richard Purdie <richard.purdie@linuxfoundation.org>]

Unfortunately whilst reruning configure and make against a project will mostly
work there are situations where it does not correctly do the right thing.

In particular, eglibc and gcc will fail out with errors where settings
do not match a previously built configuration. It could be argued they are
broken but the situation is what it is. There is the possibility of more subtle
errors too.

This patch adds a "make distclean" call to recipes where configure is
rerunning and the sstate checksum for do_configure has changed. We could
simply use a stamp but saving out the previous configuration checksum
adds some data at no real overhead.

If we find there are things out there which don't have a "distclean" target,
we can disable this behaviour with CONFIGURESTAMPFILE = "" in the recipe,
or users could disable it globally.

[YOCTO #2774]
[YOCTO #2848]

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
---
diff --git a/meta/classes/autotools.bbclass b/meta/classes/autotools.bbclass
index 4c4bf87..1ab2e0c 100644
--- a/meta/classes/autotools.bbclass
+++ b/meta/classes/autotools.bbclass
@@ -89,7 +89,16 @@ oe_runconf () {
 
 AUTOTOOLS_AUXDIR ?= "${S}"
 
+CONFIGURESTAMPFILE = "${WORKDIR}/configure.sstate"
+
 autotools_do_configure() {
+	if [ -n "${CONFIGURESTAMPFILE}" -a -e "${CONFIGURESTAMPFILE}" ]; then
+		if [ "`cat ${CONFIGURESTAMPFILE}`" != "${BB_TASKHASH}" ]; then
+			echo "Previously configured build detected, running make distclean"
+			oe_runmake distclean
+		fi
+	fi
+
 	case ${PN} in
 	autoconf*)
 	;;
@@ -180,6 +189,9 @@ autotools_do_configure() {
 	else
 		bbnote "nothing to configure"
 	fi
+	if [ -n "${CONFIGURESTAMPFILE}" ]; then
+		echo ${BB_TASKHASH} > ${CONFIGURESTAMPFILE}
+	fi
 }
 
 autotools_do_install() {