Merge #333: cmake: Do not re-write obj/build.h unnecessarily

ef1744a fixup! cmake: Add `GenerateBuildInfo.cmake` script (Hennadii Stepanov)

Pull request description:

ACKs for top commit:
  TheCharlatan:
    ACK ef1744a

Tree-SHA512: 57d6d41dbde75c18775ae9c46dd3c9063f39b2162941bbb852876b4b30c3c8ecfbe1f052d8c19ca34a92673ff644e3e252dd77b982c1c8f5bf6d951c9e994689

cmake/script/GenerateBuildInfo.cmake

@@ -102,14 +102,14 @@ if(NOT "$ENV{BITCOIN_GENBUILD_NO_GIT}" STREQUAL "1")
 endif()
 
 if(GIT_TAG)
-  set(NEWINFO "#define BUILD_GIT_TAG \"${GIT_TAG}\"\n")
+  set(NEWINFO "#define BUILD_GIT_TAG \"${GIT_TAG}\"")
 elseif(GIT_COMMIT)
-  set(NEWINFO "#define BUILD_GIT_COMMIT \"${GIT_COMMIT}\"\n")
+  set(NEWINFO "#define BUILD_GIT_COMMIT \"${GIT_COMMIT}\"")
 else()
-  set(NEWINFO "// No build information available\n")
+  set(NEWINFO "// No build information available")
 endif()
 
 # Only update the header if necessary.
 if(NOT "${INFO}" STREQUAL "${NEWINFO}")
-  file(WRITE ${BUILD_INFO_HEADER_PATH} ${NEWINFO})
+  file(WRITE ${BUILD_INFO_HEADER_PATH} "${NEWINFO}\n")
 endif()