Error Compiling Postgres

If I do a straight
./configure
gmake
gmake install

I'm able to compile and Install postgresql. But if I do the following:

CFLAGS="-O2 -march=i586 -funroll-loops" CXXFLAGS="-O2 -march=i586
-funroll-loops -felide-constructors -fno-exceptions -fno-rtti" ./configure
--prefix=/usr --includedir=/usr/include --lib-dir= --localstatedir=/var
--docdir=/usr/share/doc --sysconfdir=/etc --mandir=/usr/share/man
--disable-shared --disable-debug --disable-nls --enable-syslog --without-tcl
--without-perl --without-python --with-CXX --with-pam
gmake
gmake install

I get the following error.

make[2]: Entering directory
`/var/tmp/postgresql-7.3.3/src/backend/utils/mb/conversion_procs/ascii_and_m
ic'
/bin/sh ../../../../../../config/install-sh -c -m 755
/usr/lib/postgresql/ascii_and_mic.so
install: /usr/lib/postgresql/ascii_and_mic.so does not exist
make[2]: *** [install] Error 1
make[2]: Leaving directory
`/var/tmp/postgresql-7.3.3/src/backend/utils/mb/conversion_procs/ascii_and_m
ic'
make[1]: *** [install] Error 2
make[1]: Leaving directory
`/var/tmp/postgresql-7.3.3/src/backend/utils/mb/conversion_procs'
make: *** [install] Error 2
make: Leaving directory `/var/tmp/postgresql-7.3.3/src'

Am I missing something in the ./configure?