Use qmake -query QT_INSTALL_PLUGINS to find install location

Fallback for Qt 5.

.github/workflows/build.yml

@@ -52,8 +52,7 @@ jobs:
           -DUSE_SHARED_ZLIB=on \
           -DUSE_SHARED_PIXMAN=on \
           -DUSE_SHARED_FREETYPE=on \
-          -DUSE_SHARED_HARFBUZZ=on \
-          -DQT_PLUGIN_PATH=`qmake -query QT_INSTALL_PLUGINS`
+          -DUSE_SHARED_HARFBUZZ=on
         cmake --build build --config Release
         sudo cmake --install build --config Release
 

CMakeLists.txt

@@ -33,27 +33,22 @@ target_link_libraries(qaseprite
 set(QT_PLUGIN_PATH "" CACHE STRING "Install location for Qt plugins")
 
 if(NOT QT_PLUGIN_PATH)
+  set(QT_INSTALL_PREFIX ${QT${QT_VERSION_MAJOR}_INSTALL_PREFIX})
+  set(QT_INSTALL_PLUGINS ${QT${QT_VERSION_MAJOR}_INSTALL_PLUGINS})
+
   if(DEFINED ENV{QT_PLUGIN_PATH})
     set(QT_PLUGIN_PATH $ENV{QT_PLUGIN_PATH})
+  elseif(QT_INSTALL_PREFIX AND QT_INSTALL_PLUGINS)
+    set(QT_PLUGIN_PATH "${QT_INSTALL_PREFIX}/${QT_INSTALL_PLUGINS}")
   else()
-    set(QT_INSTALL_PREFIX ${QT${QT_VERSION_MAJOR}_INSTALL_PREFIX})
-    set(QT_INSTALL_PLUGINS ${QT${QT_VERSION_MAJOR}_INSTALL_PLUGINS})
-
-    # If QT_INSTALL_PREFIX is empty, try to derive it from QT_DIR, cutting off the
-    # last three components ("lib/cmake/Qt5") from the path
-    if(NOT QT_INSTALL_PREFIX)
-      set(QT_INSTALL_PREFIX ${QT_DIR})
-      get_filename_component(QT_INSTALL_PREFIX ${QT_INSTALL_PREFIX} DIRECTORY)
-      get_filename_component(QT_INSTALL_PREFIX ${QT_INSTALL_PREFIX} DIRECTORY)
-      get_filename_component(QT_INSTALL_PREFIX ${QT_INSTALL_PREFIX} DIRECTORY)
+    find_program(QT_QMAKE_EXECUTABLE NAMES "qmake" "qmake-qt5" "qmake.exe")
+    if(QT_QMAKE_EXECUTABLE)
+      execute_process(COMMAND "${QT_QMAKE_EXECUTABLE}" "-query" "QT_INSTALL_PLUGINS"
+                      OUTPUT_VARIABLE QT_PLUGIN_PATH
+                      OUTPUT_STRIP_TRAILING_WHITESPACE)
+    else()
+      message(FATAL_ERROR "Cannot find qmake executable")
     endif()
-
-    # If QT_INSTALL_PLUGINS is empty, set it to "plugins"
-    if(NOT QT_INSTALL_PLUGINS)
-      set(QT_INSTALL_PLUGINS "plugins")
-    endif()
-
-    set(QT_PLUGIN_PATH "${QT_INSTALL_PREFIX}/${QT_INSTALL_PLUGINS}")
   endif()
   set(QT_PLUGIN_PATH "${QT_PLUGIN_PATH}" CACHE STRING "Install location for Qt plugins" FORCE)
 endif()