Allow for override of PERL_BIN and PP_BIN

.travis.yml

@@ -53,6 +53,8 @@ matrix:
           env:
             - TARGET=main
             - WXDIR=$HOME/wx302
+            - PERL_BIN=$HOME/perl5/perlbrew/perls/slic3r-perl/bin/perl
+            - PP_BIN=$HOME/perl5/perlbrew/perls/slic3r-perl/bin/pp
           cache:
             directories:
               - $HOME/boost_1_63_0

package/linux/make_archive.sh

@@ -46,8 +46,12 @@ resourcefolder=$appfolder
 echo "Appfolder: $appfolder, archivefolder: $archivefolder"
 
 # Our slic3r dir and location of perl
-PERL_BIN=$(which perl)
-PP_BIN=$(which pp)
+if [[ ! -z "$PERL_BIN" ]]; then
+    PERL_BIN=$(which perl)
+fi
+if [[! -z "$PP_BIN" ]]; then
+    PP_BIN=$(which pp)
+fi
 SLIC3R_DIR="./"
 
 if [[ -d "${appfolder}" ]]; then