build: fix unbound variable in configure

Commentary by db:

This missing initialization caused configure to crash, and hence the
build to fail in environments without cppcheck.

1 files changed, 1 insertions, 0 deletions

diff --git a/configure b/configure
index 364854f3..c0a550c7 100755
--- a/configure
+++ b/configure
@@ -651,6 +651,7 @@ if command -v cppcheck > /dev/null; then
     have_cppcheck=1
     printf "Yes.\n"
 else
+    have_cppcheck=0
     printf "No.\n"
 fi