only require git if the source looks like it was checked out from git, otherwise don't attempt to manage the submodules

Author: db48x

configure

@@ -301,7 +301,17 @@ step_msg "looking for build programs"
 probe_need CFG_PERL        perl
 probe_need CFG_PYTHON      python python2.6 python2 python3
 probe_need CFG_CURL        curl
-probe_need CFG_GIT         git
+
+# If we have no git directory then we are probably a tarball distribution
+# and shouldn't attempt to load submodules
+if [ ! -e ${CFG_SRC_DIR}.git ]
+then
+    msg "git: no git directory. disabling submodules"
+    CFG_DISABLE_MANAGE_SUBMODULES=1
+else
+    probe_need CFG_GIT              git
+fi
+
 probe CFG_CLANG            clang++
 probe CFG_GCC              gcc
 probe CFG_LLVM_CONFIG      llvm-config