Bugreport configure ppp without '--with-openssl'

Hi,

I updated ppp-2.4.9 to ppp-2.5.0.
I have may found an issue using pkg-config to find openssl includes and libs.
After calling autogen.sh, we call configure with a lot of environment variables.
PATH=... CC=... CFLAGS=... LDFLAGS=...
PKG_CONFIG_PATH=PATH_TO_PKG_CONFIG_FILES 
configure --host=mips-34kc-linux-gnu --build=i486-linux-gnu

As you can see we do cross-compilation and don't pass --with-openssl
During configure, default ssl dirs are checked but no ssl.h file could be found.
Btw. On cross-compile we should skip checking default locations.
However the variable found is still false.
Then we come to following if:
if test "${with_openssl}" != "no" && test ! ${found}
For some reason we don't go into the if condition to use pkg-config to get
openssl includes and libs.
I think the "test ! ${found}" should be changed to "test ${found} == false".
"test ! ${somevar}" seems to be true, if somevar does not exists. It
does not check the content of the variable.

Here are some tests I made:
    foo=true
    if test ! ${foo}
    then :
        printf "%s\n" "in if test ! foo=true" >&6
    fi
    
    if test ${foo}
    then :
        printf "%s\n" "in if test foo=true" >&6
    fi
    
    foo=false
    
    if test ! ${foo}
    then :
        printf "%s\n" "in if test ! foo=false " >&6
    fi
    
    if test ${foo}
    then :
        printf "%s\n" "in if test foo=false " >&6
    fi
    
    if test ${foobarbaz}
    then :
        printf "%s\n" "in if test foobarbaz " >&6
    fi
    if test ! ${foobarbaz}
    then :
        printf "%s\n" "in if test ! foobarbaz " >&6
    fi
    
    On terminal I see following lines:
    in if test foo=true
    in if test foo=false
    in if test ! foobarbaz

Therefore I propose following patch (based on tag ppp-2.5.0)
--- a/m4/ax_check_openssl.m4
+++ b/m4/ax_check_openssl.m4
@@ -70,7 +70,7 @@ AC_DEFUN([AX_CHECK_OPENSSL], [
            ])
        done])
      
-    AS_IF([test "${with_openssl}" != "no" && test ! ${found}], [  
+    AS_IF([test "${with_openssl}" != "no" && test ${found} == false], [
        # if pkg-config is installed and openssl has installed a .pc file,
        # then use that information and don't search ssldirs
        AC_PATH_PROG([PKG_CONFIG], [pkg-config])

May you can check this.

At the moment, we use autoconf version 2.72c

If you need more details, don't hesitate to contact me.

Best regards,
Stefan Scheibner
Software engineer