When /usr/ccs/bin/as is not found configure defaults to the C++ compiler
/........./bin/CC as the assembler of choice, this fails in mysterious ways
during the build, I think if "as" is not found, configure should fail.

Here is what happens:
configure:24894: checking for as
configure:24927: result: no
configure:25194: Rewriting AS to "/java/devtools/i386/SUNWspro/SS12u1/prod/bin/CC"

/java/devtools/i386/SUNWspro/SS12u1/prod/bin/CC -xarch=amd64 -o solaris_x86_64.o /tmp/ksrini/tl/hotspot/src/os_cpu/solaris_x86/vm/solaris_x86_64.s
.......

ld: fatal: file solaris_x86_32.o: not an ELF object
ld: fatal: file processing errors. No output written to solaris_x86_32.o
gmake[6]: *** [solaris_x86_32.o] Error 1
gmake[6]: *** Waiting for unfinished jobs....
gmake[5]: *** [the_vm] Error 2
gmake[4]: *** [product] Error 2
gmake[3]: *** [generic_build2] Error 2
gmake[2]: *** [product] Error 2
gmake[1]: *** [/w/lthudson/hudson-data/jobs/jdk8-lt-jdk-build/workspace/build/solaris-x86-normal-clientANDserver-release/hotspot/_hotspot.timestamp] Error 2

and finally:
% touch foo.s
% /java/devtools/i386/SUNWspro/SS12u1/bin/CC foo.s -o foo.o
ld: fatal: file foo.o: not an ELF object
ld: fatal: file processing errors. No output written to foo.o