(conan-io#8592) Fix libjpeg-turbo build for Android

It didn't work for Android/armv7 because the recipe specifies
CMAKE_SYSTEM_PROCESSOR=armv7 which is not known to Android NDK CMake scripts.
However the NDK toolchain does not require this variable (it sets the variable
itself), so it does not need to be specified at all.

recipes/libjpeg-turbo/all/CMakeLists.txt

@@ -5,4 +5,9 @@ project(cmake_wrapper)
 include(conanbuildinfo.cmake)
 conan_basic_setup(NO_OUTPUT_DIRS)
 
+if(NOT CMAKE_SYSTEM_PROCESSOR)
+    set(CMAKE_SYSTEM_PROCESSOR ${CONAN_LIBJPEG_SYSTEM_PROCESSOR})
+endif()
+
+
 add_subdirectory("source_subfolder")

recipes/libjpeg-turbo/all/conanfile.py

@@ -123,7 +123,7 @@ def _configure_cmake(self):
                 "armv8": "aarch64",
                 "armv8.3": "aarch64",
             }.get(str(self.settings.arch), str(self.settings.arch))
-            self._cmake.definitions["CMAKE_SYSTEM_PROCESSOR"] = cmake_system_processor
+            self._cmake.definitions["CONAN_LIBJPEG_SYSTEM_PROCESSOR"] = cmake_system_processor
 
         self._cmake.configure()
         return self._cmake