Out-of-tree compilation seems broken in HEAD (plpgsql)

$ mkdir build
$ cd build
$ ../PostgreSQL.dev/configure
$ make
[...]
gcc -O2 -Wall -Wmissing-prototypes -Wpointer-arith
-Wdeclaration-after-statement -Wendif-labels -fno-strict-aliasing
-fwrapv -fpic -I/home/marko/src/build/../PostgreSQL.dev/src/pl/plpgsql/src
-I../../../../src/include
-I/home/marko/src/build/../PostgreSQL.dev/src/include -D_GNU_SOURCE
-c -o pl_comp.o
/home/marko/src/build/../PostgreSQL.dev/src/pl/plpgsql/src/pl_comp.c
/home/marko/src/build/../PostgreSQL.dev/src/pl/plpgsql/src/pl_comp.c:20:21:
error: pl_gram.h: No such file or directory

-- 
marko