In [1] Ryan Schmidt reported a problem on macports [2] with notmuch
finding an existing installed version of notmuch.h during the build.
This is a partial fix; the user might also specify -I in CFLAGS.
[1]: id:
7851CAB5-4556-4931-A0A2-
37003E56C927@ryandesign.com
[2]: The problem does not arise when notmuch.h is installed into a
"system" include path that the compiler searches by default.