Make the configure step more reliable

Iyt appears that in cross compile environments the location of the
"current" directory cannot be assumed. This fix makes it explicit.

Author: Dmitri Toubelis

CHANGES

@@ -1,6 +1,8 @@
 v3.x.y - YYYY-MMM-DD (to be released)
 -------------------------------------
 
+  - Use explicit path for cross-compile environments.
+    [Issue #2485 - @dtoubelis]
   - Fix: FILES variable does not use multipart part name for key
     [Issue #2377 - @martinhsv]
   - Replaces put with setenv in SetEnv action

configure.ac

@@ -55,7 +55,7 @@ AC_PROG_MAKE_SET
 # AX_CXX_COMPILE_STDCXX_11(,mandatory)
 
 # Check for libinjection
-if ! test -f "others/libinjection/src/libinjection_html5.c"; then
+if ! test -f "${srcdir}/others/libinjection/src/libinjection_html5.c"; then
 AC_MSG_ERROR([\