[build] check more programs in configure.ac

- to have right paths
- to detect future dependencies that will be needed by some scripts

configure.ac

@@ -83,10 +83,15 @@ AC_ARG_ENABLE([appimage],
               [AEGISUB_APPIMAGE_ENABLED=$enableval],
               [AEGISUB_APPIMAGE_ENABLED=no])
 AS_IF([test "x$AEGISUB_APPIMAGE_ENABLED" = "xyes"], [
+    # Check more binaries
+    AC_PATH_PROG([PATCHELF], [patchelf])
+    AC_PATH_PROG([WGET], [wget])
+    AC_PATH_PROG([CHMOD], [chmod])
+
     # Download the AppImage creation tool, transforms the AppDir into an AppImage
     AC_MSG_CHECKING([Downloading AppImage creation tool])
-    wget https://github.com/probonopd/AppImageKit/releases/download/continuous/appimagetool-`arch`.AppImage -O tools/appimagetool.AppImage -o config.wget.log
-    chmod 00700 tools/appimagetool.AppImage
+    $WGET https://github.com/probonopd/AppImageKit/releases/download/continuous/appimagetool-`arch`.AppImage -O tools/appimagetool.AppImage -o config.wget.log
+    $CHMOD 00700 tools/appimagetool.AppImage
     AS_IF([test $? -eq 0 ], [
         AC_MSG_RESULT([done])
     ], [
@@ -95,8 +100,8 @@ AS_IF([test "x$AEGISUB_APPIMAGE_ENABLED" = "xyes"], [
 
     # Downlaod the AppDir management tool, create the AppDir
     AC_MSG_CHECKING([Downloading LinuxDeploy creation tool])
-    wget https://martinm.iiens.net/linuxdeploy -O tools/linuxdeploy -a config.wget.log
-    chmod 00700 tools/linuxdeploy
+    $WGET https://martinm.iiens.net/linuxdeploy -O tools/linuxdeploy -a config.wget.log
+    $CHMOD 00700 tools/linuxdeploy
     AS_IF([test $? -eq 0 ], [
         AC_MSG_RESULT([done])
     ], [