Don't require SDL2 or OGL for building the servers.

Requiring SDL2 was masking needing to add -lpthread explicitly.

(cherry-picked from commit fd34fe8497)

CMakeLists.txt

@@ -76,9 +76,11 @@ else()
 	message(WARNING "You are cross-compiling. Skipping IEEE 754 test.")
 endif()
 
-find_package(OpenGL REQUIRED)
-find_package(GLEW REQUIRED)
-find_package(SDL2 2.0.4 REQUIRED)
+if(ENABLE_GAME OR ENABLE_TESTS)
+	find_package(OpenGL REQUIRED)
+	find_package(GLEW REQUIRED)
+	find_package(SDL2 2.0.4 REQUIRED)
+endif(ENABLE_GAME OR ENABLE_TESTS)
 find_package(Crypto 1.0 REQUIRED)
 find_package(Boost 1.56 REQUIRED COMPONENTS iostreams program_options regex system random)
 

src/CMakeLists.txt

@@ -101,6 +101,7 @@ set(server-external-libs
 	${Boost_RANDOM_LIBRARY}
 	${CRYPTO_LIBRARY}
 	${MYSQL_LIBS}
+	-lpthread
 )
 
 if(ENABLE_FRIBIDI AND FRIBIDI_FOUND)