check if BuildInfo.h is outdated

cmake/scripts/buildinfo.cmake

@@ -19,7 +19,7 @@ endif()
 
 execute_process(
 	COMMAND git --git-dir=${ETH_SOURCE_DIR}/.git --work-tree=${ETH_SOURCE_DIR} rev-parse HEAD
-	OUTPUT_VARIABLE ETH_COMMIT_HASH
+	OUTPUT_VARIABLE ETH_COMMIT_HASH OUTPUT_STRIP_TRAILING_WHITESPACE
 ) 
 
 if (NOT ETH_COMMIT_HASH)
@@ -28,7 +28,7 @@ endif()
 
 execute_process(
 	COMMAND git --git-dir=${ETH_SOURCE_DIR}/.git --work-tree=${ETH_SOURCE_DIR} diff --shortstat	
-	OUTPUT_VARIABLE ETH_LOCAL_CHANGES
+	OUTPUT_VARIABLE ETH_LOCAL_CHANGES OUTPUT_STRIP_TRAILING_WHITESPACE
 )
 
 if (ETH_LOCAL_CHANGES)
@@ -37,5 +37,25 @@ else()
 	set(ETH_CLEAN_REPO 1)
 endif()
 
-configure_file("${ETH_SOURCE_DIR}/BuildInfo.h.in" "${ETH_DST_DIR}/BuildInfo.h")
+set(INFILE "${ETH_SOURCE_DIR}/BuildInfo.h.in")
+set(TMPFILE "${ETH_DST_DIR}/BuildInfo.h.tmp")
+set(OUTFILE "${ETH_DST_DIR}/BuildInfo.h")
+
+# create outfile if it doesn't exist
+if (NOT (EXISTS ${OUTFILE}))
+	execute_process(COMMAND touch ${OUTFILE})
+endif()
+
+configure_file("${INFILE}" "${TMPFILE}")
+
+execute_process(
+	COMMAND diff "${OUTFILE}" "${TMPFILE}"
+	OUTPUT_VARIABLE ETH_FILE_OUTDATED
+)
+
+if (ETH_FILE_OUTDATED)
+	execute_process(COMMAND mv "${TMPFILE}" "${OUTFILE}")
+else()
+	execute_process(COMMAND rm "${TMPFILE}")
+endif()