attempt to fix make.tcl for use with tcl8.6 (no zipfs available)

src/make.tcl

@@ -2839,6 +2839,9 @@ foreach vfstail $vfs_tails {
                         #zipfs mkimg replaces the entire zipped vfs in the runtime - so we need the original data to be part of our targetvfs.
                         puts stdout "building $vfsname.new with zipfs vfsdir:$vfstail cwd: [pwd]"
                         file mkdir $targetvfs
+
+                        if {[info commands ::tcl::zipfs::mount] ne ""} {
+
                             set rtmountpoint //zipfs:/rtmounts/$runtime_fullname 
 
                             if {![file exists $rtmountpoint]} {
@@ -2885,11 +2888,17 @@ foreach vfstail $vfs_tails {
                                     punk::zip::extract_preamble $building_runtime $raw_runtime
                                 }
                             } else {
-                            #the input building_runtime wasn't mountable - so presumably a plain executable
+                                #the input building_runtime wasn't mountable as a zip - so presumably a plain executable
                                 #set building_runtime $buildfolder/build_$runtime_fullname ;#working copy of runtime executable - (possibly with kit/zipfs/cookfs etc attached!)
                                 #set raw_runtime $buildfolder/raw_$runtime_fullname
                                 file copy -force $building_runtime $raw_runtime
                             }
+                        } else {
+                            #tcl we are calling with doesn't have zipfs - can't mount
+                            puts stderr "WARNING: tcl shell '[info nameofexecutable]' being used to build doesn't have zipfs - falling back to punk::zip::extract_preamble"
+                            punk::zip::extract_preamble $building_runtime $raw_runtime $buildfolder/extracted_$runtime_fullname.zip
+                            merge_over $buildfolder/extracted_$runtime_fullname.zip $targetvfs
+                        }
 
                         merge_over $sourcefolder/vfs/_vfscommon.vfs $targetvfs