appveyor/autotools: link with openssl by passing LDFLAGS/CFLAGS

This never works, hence green tests in production. and now it works:
https://ci.appveyor.com/project/azat/libevent/build/2.1.5.100/job/eib4xqfb7d3ruo16
(look by /"evthread_win32.c")

appveyor.yml

@@ -46,9 +46,10 @@ build_script:
   - ps: |
       if ($env:EVENT_BUILD_METHOD -eq 'autotools') {
         $env:PATH="$env:CYG_ROOT\bin;C:\MinGW\bin;$($env:PATH)"
-        bash -lc "echo 'C:\MinGW   /mingw' > /etc/fstab"
+        bash -lc "echo 'C:\MinGW /mingw' > /etc/fstab"
+        bash -lc "echo 'C:\OpenSSL-Win32 /ssl' >> /etc/fstab"
         $env:APPVEYOR_BUILD_FOLDER = $env:APPVEYOR_BUILD_FOLDER -replace "\\", "/"
-        bash -lc "exec 0</dev/null; exec 2>&1; cd $env:APPVEYOR_BUILD_FOLDER; bash -x ./autogen.sh && ./configure $env:EVENT_CONFIGURE_OPTIONS && make && make verify"
+        bash -lc "exec 0</dev/null; exec 2>&1; cd $env:APPVEYOR_BUILD_FOLDER; bash -x ./autogen.sh && ./configure LDFLAGS='-L/ssl -L/ssl/lib -L/ssl/lib/MinGW' CFLAGS=-I/ssl/include $env:EVENT_CONFIGURE_OPTIONS && make && make verify"
       } else {
         md build
         cd build