The following screendump should say it all:

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# rpm -qi build
[...]
Description :
This package provides a script for building RPMs for SUSE Linux in a
chroot environment.

Requires: build-mkbaselibs
Recommends: build-mkdrpms
Distribution: openSUSE:Tools / openSUSE_11.4
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Needless to say that rpm -q --requires / --recommends does not list
build-mkbaselibs and build-mkdrpms.

This SR fixes this bug.

Note: the Recommends is only enabled on distributions that support it.