First, configure fails to detect that gcc produces 64-bit binaries, leading to

libtool: compile:  gcc -DHAVE_CONFIG_H -I. -I../.. -Wall -D_BSD_SOURCE -D_GNU_SOURCE -I../.. -DOIL_ENABLE_UNSTABLE_API -g -O2 -MT libi386_la-argb_paint_i386.lo -MD -MP -MF .deps/libi386_la-argb_paint_i386.Tpo -c argb_paint_i386.c  -fno-common -DPIC -o .libs/libi386_la-argb_paint_i386.o
/var/folders/WC/WCQfew6LEaqrFEF+j4W8CE+++TI/-Tmp-//ccgjScsQ.s:52:Incorrect register `%rax' used with `l' suffix
/var/folders/WC/WCQfew6LEaqrFEF+j4W8CE+++TI/-Tmp-//ccgjScsQ.s:58:Incorrect register `%rax' used with `l' suffix
make[3]: *** [libi386_la-argb_paint_i386.lo] Error 1
make[2]: *** [all-recursive] Error 1
make[1]: *** [all-recursive] Error 1
make: *** [all] Error 2

adding --host=x86_64-apple-darwin lets the build get further, failing at

libtool: link: ( cd ".libs" && rm -f "liboilfunctions.la" && ln -s "../liboilfunctions.la" "liboilfunctions.la" )
/bin/sh ../libtool --tag=CC   --mode=link gcc  -g -O2 -no-undefined -export-symbols-regex 'oil_'  -o liboiltmp1.la -rpath /usr/local/lib liboiltmp.lo liboilfunctions.la   
libtool: link: link -dump -symbols  .libs/liboiltmp.o   ./.libs/liboilfunctions.a |  | /usr/bin/sed 's/.* //' | sort | uniq > .libs/liboiltmp1.exp
../libtool: eval: line 947: syntax error near unexpected token `|'
../libtool: eval: line 947: `link -dump -symbols  .libs/liboiltmp.o   ./.libs/liboilfunctions.a |  | /usr/bin/sed 's/.* //' | sort | uniq > .libs/liboiltmp1.exp'
make[3]: *** [liboiltmp1.la] Error 1
make[2]: *** [all-recursive] Error 1
make[1]: *** [all-recursive] Error 1
make: *** [all] Error 2