Replace read time checks with run time ones
Replace read time checks with run time ones

ifeq being processed on Makefile read so it's not possible to build
html version of docs or someone else without having all toolchain
installed. Since TeX one is quite big (up to 2.6GiB on some systems)
it makes work on documentation kind of pain.

robertkowalski/couch-doc-test,kxepal/couchdb-documentation,andywenk/couchdb-documentation,robertkowalski/couch-doc-test,KimStebel/couchdb-documentation,kxepal/couchdb-documentation,andywenk/couchdb-documentation,cloudant/couchdb-documentation,cloudant/couchdb-documentation,micah/couchdb-documentation,andywenk/couchdb-documentation,robertkowalski/couch-doc-test,KimStebel/couchdb-documentation,kxepal/couchdb-documentation,micah/couchdb-documentation,micah/couchdb-documentation,KimStebel/couchdb-documentation