Sort variables by name when writing ninja files
Sort variables by name when writing ninja files

Regenerating build.ninja.in was non-deterministic, sort the maps
of name, value pairs before writing them.

Change-Id: I825734162b1adebc88ddb19d912751108322091e

danw/blueprint,google/blueprint,yuhangwang/blueprint,danw/blueprint,yuhangwang/blueprint,colincross/blueprint,google/blueprint,colincross/blueprint,Tiger66639/blueprint,jgennis/blueprint,jgennis/blueprint,Tiger66639/blueprint