Installworld failure on RELENG_9

[Chris H]

Greetings,
 I've used BSD exclusively since the early 80's, and this is my first
experience with a build(world|kernel) || install(world|kernel) fail.
That said, after installing from a 9.0 CD && syncing src && ports,
I began the process of building and installing a custom kernel, and
building & installing world.
kernel went as expected/anticipated. However, as buildworld (altho slow)
went without incident, installworld failed:

------ begin error output ---------
/usr/src/lib/csu/i386-elf/crti.S:26:25 error: machine/asm.h: No such file or directory
/usr/src/lib/csu/i386-elf/crti.S: Assembler messages:
/usr/src/lib/csu/i386-elf/crti.S:27: Error: invalid character '_' in mnemonic
*** Error code 1

Stop in /usr/src/lib/csu/i386-elf.
*** Error code 1

Stop in /usr/src/lib.
*** Error code 1

Stop in /usr/src.
*** Error code 1

Stop in /usr/src.
*** Error code 1

Stop in /usr/src.
*** Error code 1

Stop in /usr/src.
------ end error output ---------

Additional info:
FreeBSD 9.1-PRERELEASE #0 Sun Dec 16 21:27:50 PST 2012
root at ns0:/usr/obj/usr/src/sys/GENERIC i386

The only difference (aside from BSD version) was the addition of clang.
It took easily 3 times as long to complete world than past experience. :(

Thank you for all your time, and consideration.

--Chris