Disable .pc generation by default

The problem with generating a pkgconfig file via CMake is that it does
not fit the model of CMake. The `prefix` variable has to be absolute in
the .pc file, however CMake deals with paths relative to the prefix. The
final prefix can change at all times, via `CMAKE_INSTALL_PREFIX`,
`--prefix` parameter during install time, at CPack time and the
resulting deb/rpm files can be extracted anywhere as well. If one needs
a pkgconfig file for packaging purposes, both deb and rpm CPack
generators allow the user to add post-install scripts that can generate
it if necessary.

CMakeLists.txt

@@ -87,7 +87,9 @@ if(NOT CMAKE_SKIP_INSTALL_RULES)
     DESTINATION "${ctre_INSTALL_CMAKEDIR}"
     NAMESPACE ctre::)
 
-  option(ctre_ENABLE_PKGCONFIG "Install a .pc file for the project" ON)
+  option(ctre_ENABLE_PKGCONFIG "Install a .pc file for the project" OFF)
+  mark_as_advanced(ctre_ENABLE_PKGCONFIG)
+
   if(ctre_ENABLE_PKGCONFIG)
     # This can only detect issues on first configure, but it's still better
     # than nothing