README,manibuilder: Update environment overrides for DJGPP

The currently documented DJGPP setup doesn't utilize pkg-config, hence
we have to specify the presence of libpci explicitly.

Change-Id: I1e5cc9e0235fd49948edd9d39087735b8685638e
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/flashrom-stable/+/73776
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/README b/README
index ac30d6a..b9857ad 100644
--- a/README
+++ b/README
@@ -130,7 +130,9 @@
 
  Enter the flashrom directory.
 
- make CC=i586-pc-msdosdjgpp-gcc STRIP=i586-pc-msdosdjgpp-strip LIBS_BASE=../libpci-libgetopt/ strip
+ make CC=i586-pc-msdosdjgpp-gcc STRIP=i586-pc-msdosdjgpp-strip \
+	LIBS_BASE=../libpci-libgetopt/ HAS_LIBPCI=yes CONFIG_LIBPCI_LDFLAGS=-lpci \
+	strip
 
  If you like, you can compress the resulting executable with UPX: