AppVeyor: switch 64-bit Schannel Debug CMake builds to Unicode

The Schannel builds are the most useful to verify as they make the most
use of the Windows API. Classic MinGW doesn't support Unicode at all,
only MinGW-w64 and MSVC do.

Closes https://github.com/curl/curl/pull/5843

appveyor.yml

@@ -31,6 +31,7 @@ environment:
         PRJ_CFG: Release
         OPENSSL: OFF
         SCHANNEL: ON
+        ENABLE_UNICODE: OFF
         HTTP_ONLY: OFF
         TESTING: OFF
         SHARED: ON
@@ -43,6 +44,7 @@ environment:
         PRJ_CFG: Release
         OPENSSL: ON
         SCHANNEL: OFF
+        ENABLE_UNICODE: OFF
         HTTP_ONLY: OFF
         TESTING: OFF
         SHARED: ON
@@ -55,6 +57,7 @@ environment:
         PRJ_CFG: Release
         OPENSSL: OFF
         SCHANNEL: ON
+        ENABLE_UNICODE: OFF
         HTTP_ONLY: OFF
         TESTING: OFF
         SHARED: OFF
@@ -67,6 +70,7 @@ environment:
         PRJ_CFG: Debug
         OPENSSL: OFF
         SCHANNEL: OFF
+        ENABLE_UNICODE: OFF
         HTTP_ONLY: OFF
         TESTING: ON
         SHARED: OFF
@@ -79,6 +83,7 @@ environment:
         PRJ_CFG: Debug
         OPENSSL: OFF
         SCHANNEL: ON
+        ENABLE_UNICODE: ON
         HTTP_ONLY: OFF
         TESTING: ON
         SHARED: OFF
@@ -91,6 +96,7 @@ environment:
         PRJ_CFG: Debug
         OPENSSL: OFF
         SCHANNEL: OFF
+        ENABLE_UNICODE: OFF
         HTTP_ONLY: OFF
         TESTING: ON
         SHARED: OFF
@@ -103,6 +109,7 @@ environment:
         PRJ_CFG: Debug
         OPENSSL: OFF
         SCHANNEL: OFF
+        ENABLE_UNICODE: OFF
         HTTP_ONLY: ON
         TESTING: ON
         SHARED: OFF
@@ -115,6 +122,7 @@ environment:
         PRJ_CFG: Debug
         OPENSSL: OFF
         SCHANNEL: ON
+        ENABLE_UNICODE: ON
         HTTP_ONLY: OFF
         TESTING: ON
         SHARED: OFF
@@ -128,6 +136,7 @@ environment:
         PRJ_CFG: Debug
         OPENSSL: OFF
         SCHANNEL: ON
+        ENABLE_UNICODE: ON
         HTTP_ONLY: OFF
         TESTING: ON
         SHARED: OFF
@@ -141,6 +150,7 @@ environment:
         PRJ_CFG: Debug
         OPENSSL: OFF
         SCHANNEL: ON
+        ENABLE_UNICODE: OFF
         HTTP_ONLY: OFF
         TESTING: ON
         SHARED: OFF
@@ -154,6 +164,7 @@ environment:
         PRJ_CFG: Debug
         OPENSSL: OFF
         SCHANNEL: OFF
+        ENABLE_UNICODE: OFF
         HTTP_ONLY: OFF
         TESTING: ON
         SHARED: OFF
@@ -250,6 +261,7 @@ build_script:
         -DBUILD_TESTING=%TESTING%
         -DCURL_WERROR=ON
         -DENABLE_DEBUG=ON
+        -DENABLE_UNICODE=%ENABLE_UNICODE%
         -DCMAKE_RUNTIME_OUTPUT_DIRECTORY_RELEASE=""
         -DCMAKE_RUNTIME_OUTPUT_DIRECTORY_DEBUG=""
         -DCMAKE_INSTALL_PREFIX="C:/CURL"