Fix linking with BUILD_SHARED_LIBS=ON default in EAPI-7.

--- a/src/game/STFH/CMakeLists.txt	2017-08-28 21:43:54.000000000 +0200
+++ b/src/game/STFH/CMakeLists.txt	2021-02-27 20:58:35.523503983 +0100
@@ -10,5 +10,5 @@
     source.cpp
 )
 
-add_library(STFH ${STFHSRC})
+add_library(STFH STATIC ${STFHSRC})
 
--- a/src/game/MTFH/CMakeLists.txt	2017-08-28 21:43:54.000000000 +0200
+++ b/src/game/MTFH/CMakeLists.txt	2021-02-27 20:58:48.451565823 +0100
@@ -9,5 +9,5 @@
     menumanager.cpp
     menuitemview.cpp)
 
-add_library(MTFH ${MTFHSRC})
+add_library(MTFH STATIC ${MTFHSRC})
 
--- a/src/game/MiniCore/CMakeLists.txt	2017-08-28 21:43:54.000000000 +0200
+++ b/src/game/MiniCore/CMakeLists.txt	2021-02-27 20:59:01.267627130 +0100
@@ -82,7 +82,7 @@
 set(MiniCoreSRC ${MiniCoreSRC} Graphics/contrib/glew/glew.c)
 endif()
 
-add_library(MiniCore ${MiniCoreSRC})
+add_library(MiniCore STATIC ${MiniCoreSRC})
 
 target_link_libraries(MiniCore Qt5::Core Qt5::OpenGL Qt5::Xml OpenGL::GL)