CMake: add an include guard since files are intended to be included in other projects

contrib/Filelists.cmake

@@ -8,6 +8,8 @@
 # The intention is to provide greater flexibility to users to 
 # create their own targets using the *_SRCS variables.
 
+include_guard(GLOBAL)
+
 set(lwipcontribexamples_SRCS
     ${LWIP_CONTRIB_DIR}/examples/httpd/fs_example/fs_example.c
     ${LWIP_CONTRIB_DIR}/examples/httpd/ssi_example/ssi_example.c

contrib/ports/CMakeCommon.cmake

@@ -1,3 +1,5 @@
+include_guard(GLOBAL)
+
 set(LWIP_CONTRIB_DIR ${LWIP_DIR}/contrib)
 
 # ARM mbedtls support https://tls.mbed.org/

contrib/ports/unix/Filelists.cmake

@@ -8,6 +8,8 @@
 # The intention is to provide greater flexibility to users to 
 # create their own targets using the *_SRCS variables.
 
+include_guard(GLOBAL)
+
 set(lwipcontribportunix_SRCS
     ${LWIP_CONTRIB_DIR}/ports/unix/port/sys_arch.c
     ${LWIP_CONTRIB_DIR}/ports/unix/port/perf.c

contrib/ports/win32/Filelists.cmake

@@ -8,6 +8,8 @@
 # The intention is to provide greater flexibility to users to 
 # create their own targets using the *_SRCS variables.
 
+include_guard(GLOBAL)
+
 set(lwipcontribportwindows_SRCS
     ${LWIP_CONTRIB_DIR}/ports/win32/sys_arch.c
     ${LWIP_CONTRIB_DIR}/ports/win32/sio.c

src/Filelists.cmake

@@ -8,6 +8,8 @@
 # The intention is to provide greater flexibility to users to
 # create their own targets using the *_SRCS variables.
 
+include_guard(GLOBAL)
+
 set(LWIP_VERSION_MAJOR    "2")
 set(LWIP_VERSION_MINOR    "2")
 set(LWIP_VERSION_REVISION "0")

test/unit/Filelists.cmake

@@ -8,6 +8,8 @@
 # The intention is to provide greater flexibility to users to 
 # create their own targets using the *_SRCS variables.
 
+include_guard(GLOBAL)
+
 set(LWIP_TESTDIR ${LWIP_DIR}/test/unit)
 set(LWIP_TESTFILES
 	${LWIP_TESTDIR}/lwip_unittests.c