Add libm to eliminate "undefined reference to sqrt" on arm 'softfp' builds.


git-svn-id: svn+ssh://svn.freebsd.org/base/head@274851 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f
Fix build with asr driver

This was broken by r274819 as asr is not in GENERIC because its not 64bit
safe.

MFC after:	1 month
X-MFC-With:	r274819
Sponsored by:	Multiplay


git-svn-id: svn+ssh://svn.freebsd.org/base/head@274852 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f