[PATCH] configure: check for bison, flex before dtc submodule build

[Claudio Fontana]

if fdt is required, and the system DTC (libfdt) is not usable,
check for the dtc submodule requirements before trying to build it,
and error out with a helpful message in case the dependencies are not met.

Signed-off-by: Claudio Fontana <address@hidden>
---
 configure | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/configure b/configure
index 22870f3867..68b95b8e94 100755
--- a/configure
+++ b/configure
@@ -4276,6 +4276,14 @@ EOF
           git_submodules="${git_submodules} dtc"
       fi
       if test -d "${source_path}/dtc/libfdt" || test -e "${source_path}/.git" 
; then
+          for binary in ${BISON:-bison} ${LEX:-flex} ; do
+              if ! has $binary ; then
+                  error_exit "DTC (libfdt) version >= 1.4.2 not present on the 
system,\n" \
+                             "and using the dtc submodule replacement requires 
'${binary}'.\n" \
+                             "Please install the DTC (libfdt) devel 
package,\n" \
+                             "or the required binary '${binary}' to use the 
dtc submodule instead.\n"
+              fi
+          done
           fdt=git
           mkdir -p dtc
           if [ "$pwd_is_source_path" != "y" ] ; then
-- 
2.16.4