~/SpiderOak Hive/Software projects/git projects/FreeDesktop/libinput$ ninja -C builddir/
ninja: Entering directory `builddir/'
[1/264] Generating doxygen with a custom command.
error: tag HTML_HEADER: header file `/home/nate/SpiderOakHive/Softwareprojects/gitprojects/FreeDesktop/libinput/doc/style/header.html' does not exist
[6/264] Compiling C object 'libinput-debug-events@exe/tools_libinput-debug-events.c.o'.
ninja: build stopped: subcommand failed.
Notice how the spaces have disappeared in the ninja-generated build command: "/SpiderOak Hive/Software projects/git projects/" has become "SpiderOakHive/Softwareprojects/gitprojects"
If I move my checkout to a path with no spaces in it, like ~, the ninja command completes successfully.
$ /usr/bin/ninja --version
$ /home/nate/.local/bin/meson --version
Author: Peter Hutterer <email@example.com>
Date: Wed Nov 1 14:54:59 2017 +1000
doc: quote all paths in the doxygen file