Check if python 2 is available for crasphad

Crashpad required python 2 since the gn build system invokes python. This disables crashpad if Python2 is not detected.

CMakeLists.txt

@@ -101,7 +101,9 @@ target_link_libraries(Etterna PRIVATE libcurl)
 target_link_libraries(Etterna PRIVATE fmt::fmt)
 target_link_libraries(Etterna PRIVATE plog::plog)
 
-if(WITH_CRASHPAD)
+# If the user wants crashpad, and the target exists (in-case
+# the user wants it, but crashpad couldn't find python)
+if(WITH_CRASHPAD AND TARGET crashpad)
     target_link_libraries(Etterna PRIVATE crashpad)
 endif()
 

extern/CMakeLists.txt

@@ -47,13 +47,16 @@ add_subdirectory(zlib)
 add_subdirectory(mad-0.15.1b)
 add_subdirectory(fmt)
 add_subdirectory(plog)
-add_subdirectory(crashpad)
 
 ## Vorbis depends on ogg
 add_subdirectory(newogg)
 add_subdirectory(newvorbis)
 target_link_libraries(vorbis ogg)
 
+# Only enable crashpad if the user wants it.
+if(WITH_CRASHPAD)
+    add_subdirectory(crashpad)
+endif()
 
 if(MSVC) # Only required on Windows
     add_subdirectory(ffmpeg)

extern/crashpad/CMakeLists.txt

@@ -1,3 +1,13 @@
+# First, we check to see if the user has Python2. The crashpad gn build invokes
+# a Python2 script. We will see if we can find Python2. If we can, we will assume
+# it's on the system path, otherwise, we will notify the user, then disable crashpad.
+find_package (Python2)
+if(NOT Python2_FOUND)
+	message(WARNING " Python 2 was not found. Crashpad will be disabled. If you would like to build"
+					" crashpad, please ensure Python 2 is installed and apart of the system path.")
+	return()
+endif()
+
 # Google uses depot_tools to download and build crashpad. We will do the same.
 # This file make assumptions about where crashpad is located. Chromium uses depot_tools
 # to download and setup a directory for the crashpad/breakpad/chromium tools. We do not