Updating appveyor configuration.

Author: arobenko

.appveyor.yml

@@ -36,7 +36,7 @@ build_script:
     - if exist %BUILD_DIR% rmdir /S /Q %BUILD_DIR%
     - mkdir %BUILD_DIR%
     - cd %BUILD_DIR%
-    - cmake .. -DCMAKE_BUILD_TYPE=%CONFIGURATION% -G "NMake Makefiles" -DBOOST_ROOT="C:\Libraries\boost_1_65_1" -DBoost_USE_STATIC_LIBS=ON 
+    - cmake .. -DCMAKE_BUILD_TYPE=%CONFIGURATION% -G "NMake Makefiles" -DBOOST_ROOT="C:/Libraries/boost_1_65_1" -DBoost_USE_STATIC_LIBS=ON 
     - nmake
     - mkdir output.build
     - cd output.build

script/appveyor_install.bat

@@ -23,17 +23,17 @@ IF "%APPVEYOR_BUILD_WORKER_IMAGE%"=="Visual Studio 2015" (
     exit -1
 )
 
-set QTDIR_PREFIX=C:\Qt\%QT_VER%
+set QTDIR_PREFIX=C:/Qt/%QT_VER%
 IF "%PLATFORM%"=="x86" (
     set QTDIR_SUFFIX=
 ) ELSE (
     set QTDIR_SUFFIX=_64
 )
 
-set QTDIR=%QTDIR_PREFIX%\%QT_SUBDIR%%QTDIR_SUFFIX%
+set QTDIR=%QTDIR_PREFIX%/%QT_SUBDIR%%QTDIR_SUFFIX%
 IF NOT EXIST %QTDIR% (
     echo WARNING: %QTDIR% does not exist!!!
-    set QTDIR=%QTDIR_PREFIX%\msvc2015%QTDIR_SUFFIX%
+    set QTDIR=%QTDIR_PREFIX%/msvc2015%QTDIR_SUFFIX%
 )
 
 echo Using Qt5 from %QTDIR%