Another small thing which might be environmental... llvmjit_types.bc
is getting installed into ${prefix}/lib here, but you're looking for
it in ${prefix}/lib/postgresql:
gmake[3]: Entering directory '/usr/home/munro/projects/postgres/src/backend/lib'
/usr/bin/install -c -m 644 llvmjit_types.bc '/home/munro/install/lib'
postgres=# set jit_above_cost = 0;
SET
postgres=# set jit_expressions = on;
SET
postgres=# select 4 + 4;
ERROR: LLVMCreateMemoryBufferWithContentsOfFile(/usr/home/munro/install/lib/postgresql/llvmjit_types.bc)
failed: No such file or directory
$ mv ~/install/lib/llvmjit_types.bc ~/install/lib/postgresql/
postgres=# select 4 + 4;
?column?
----------
8
(1 row)
--
Thomas Munro
http://www.enterprisedb.com