Help needed with MakeMaker

I am building a Perl module with XS. Most of it is fairly standard, but I am
using an SQL preprocessor, so I need to precompile my C-with-embedded-SQL
into plain C before compiling the rest of the module. In other words, I need
to convert X.csql to X.c at the same time as Y.xs is converted to Y.c. I
have read the MakeMaker man page and tried a number of things (C=>"X.c Y.c",
MY::depend, etc.), but nothing quite works.

The closest attempt performed the precompile correctly but then failed to
pull in the correct headers for the XS code:

LD_RUN_PATH="/lib" cc -G B.c xxx.o /usr/lib/ppruntim.a -o
blib/arch/auto/xxx/xxx/B.so -lnsl -lsocket
"B.xs", line 1: cannot find include file: "EXTERN.h"
"B.xs", line 2: cannot find include file: "perl.h"
"B.xs", line 3: cannot find include file: "XSUB.h"
[etc.]

I'm sure there is some simple incantation I'm missing here. Any ideas?