Problem: Appveyor builds Libsodium when disabled

Solution: use if statements to avoid building it when it's disabled

appveyor.yml

@@ -65,12 +65,12 @@ install:
   - cmd: if "%Platform%"=="x64" set "CMAKE_GENERATOR=%CMAKE_GENERATOR% Win64"
   - cmd: echo "Generator='%CMAKE_GENERATOR%'"
   - cmd: echo "Platform='%Platform%'"
-  - cmd: set LIBSODIUMDIR=C:\projects\libsodium
-  - cmd: git clone --branch stable --depth 1 --quiet "https://github.com/jedisct1/libsodium.git" %LIBSODIUMDIR%
-  - cmd: msbuild /v:minimal /maxcpucount:%NUMBER_OF_PROCESSORS% /p:Configuration=%Configuration%DLL %LIBSODIUMDIR%\builds\msvc\%MSVCYEAR%\libsodium\libsodium.vcxproj
-  - cmd: set SODIUM_LIBRARY_DIR="%LIBSODIUMDIR%\bin\%Platform%\%Configuration%\%MSVCVERSION%\dynamic"
-  - cmd: set SODIUM_INCLUDE_DIR="%LIBSODIUMDIR%\src\libsodium\include"
-  - cmd: move "%SODIUM_LIBRARY_DIR%\libsodium.lib" "%SODIUM_LIBRARY_DIR%\sodium.lib"
+  - cmd: if "%WITH_LIBSODIUM%"=="ON" set LIBSODIUMDIR=C:\projects\libsodium
+  - cmd: if "%WITH_LIBSODIUM%"=="ON" git clone --branch stable --depth 1 --quiet "https://github.com/jedisct1/libsodium.git" %LIBSODIUMDIR%
+  - cmd: if "%WITH_LIBSODIUM%"=="ON" msbuild /v:minimal /maxcpucount:%NUMBER_OF_PROCESSORS% /p:Configuration=%Configuration%DLL %LIBSODIUMDIR%\builds\msvc\%MSVCYEAR%\libsodium\libsodium.vcxproj
+  - cmd: if "%WITH_LIBSODIUM%"=="ON" set SODIUM_LIBRARY_DIR="%LIBSODIUMDIR%\bin\%Platform%\%Configuration%\%MSVCVERSION%\dynamic"
+  - cmd: if "%WITH_LIBSODIUM%"=="ON" set SODIUM_INCLUDE_DIR="%LIBSODIUMDIR%\src\libsodium\include"
+  - cmd: if "%WITH_LIBSODIUM%"=="ON" move "%SODIUM_LIBRARY_DIR%\libsodium.lib" "%SODIUM_LIBRARY_DIR%\sodium.lib"
 
 clone_folder: C:\projects\libzmq
 
@@ -87,7 +87,7 @@ build:
 
 after_build:
   - cmd: cd %LIBZMQ_BUILDDIR%\bin\%Configuration%"
-  - cmd: copy "%SODIUM_LIBRARY_DIR%\libsodium.dll" .
+  - cmd: if "%WITH_LIBSODIUM%"=="ON" copy "%SODIUM_LIBRARY_DIR%\libsodium.dll" .
   - cmd: 7z a -y -bd -mx=9 libzmq.zip *.exe *.dll
   - ps: Push-AppveyorArtifact "libzmq.zip" -Filename "libzmq-${env:Platform}-${env:Configuration}.zip"