🔨 CMake Vita: Set pkgconfig path and fix prefix

1. Make CMake use VitaSDK's pkg-config wrapper.
   Fix sent upstream: https://github.com/vitasdk/vita-toolchain/pull/182

2. Work around broken `prefix` in `pkgconfig` files:
   https://github.com/vitasdk/vdpm/issues/69

.circleci/config.yml

@@ -135,7 +135,9 @@ jobs:
     working_directory: ~/repo
     steps:
       - checkout
-      - run: apk --no-cache add git cmake ninja
+      # Work around https://github.com/vitasdk/vdpm/issues/69
+      - run: mkdir -p /usr/local && ln -sf /home/user/vitasdk /usr/local/vitasdk
+      - run: apk --no-cache add git cmake ninja bash pkgconfig
       - run: cmake -S. -Bbuild -GNinja -DCMAKE_TOOLCHAIN_FILE=${VITASDK}/share/vita.toolchain.cmake -DNIGHTLY_BUILD=ON
       - run: cmake --build build -j 2
       - store_artifacts: {path: ./build/devilutionx.vpk, destination: devilutionx.vpk}

CMakeLists.txt

@@ -94,6 +94,10 @@ if(SWITCH)
 endif()
 
 if(VITA)
+  # Work around a missing setting in the toolchain file.
+  # Fix sent upstream: https://github.com/vitasdk/vita-toolchain/pull/182
+  set(PKG_CONFIG_EXECUTABLE "$ENV{VITASDK}/bin/arm-vita-eabi-pkg-config")
+
   include("$ENV{VITASDK}/share/vita.cmake" REQUIRED)
   include(vita_defs)
 endif()