Author: Vagrant Cascadian <vagrant@reproducible-builds.org>
Description: Use UTC timezone for build timestamp

While CMake respects SOURCE_DATE_EPOCH, it still can produce a
different date depending on the timezone of the running system.

Specify timezone in UTC to enable a reproducible build.

--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -49,7 +49,7 @@
   set(GENERATOR_IS_MULTI_CONFIG TRUE)
 endif()
 
-string(TIMESTAMP DEFAULT_BUILD "%Y%m%d")
+string(TIMESTAMP DEFAULT_BUILD "%Y%m%d" UTC)
 set(BUILD ${DEFAULT_BUILD} CACHE STRING "Build string (default: ${DEFAULT_BUILD})")
 
 # NOTE: On Windows, this does nothing except when using MinGW or Cygwin.