Add prefix to pkgconfig

The pkg-config program used in the CI expects the `prefix` variable to
be set in the pkgconfig file. As such, this variable is added so that
the CI can pass.

This may not affect bitbake since the pkg-config program used by bitbake
may accept a pkgconfig file without a prefix variable in it.

Signed-off-by: Sui Chen <suichen@google.com>
Change-Id: I9672597bf54044f2261f8cdc63bd21c5ebfba007
diff --git a/phosphor-ipmi-blobs.pc.in b/phosphor-ipmi-blobs.pc.in
index 1ccc785..140aeb7 100644
--- a/phosphor-ipmi-blobs.pc.in
+++ b/phosphor-ipmi-blobs.pc.in
@@ -1,3 +1,5 @@
+prefix=@prefix@
+
 Name: phosphor-ipmi-blobs
 Description: Phosphor Blob Transfer Interface
 URL: https://github.com/openbmc/phosphor-ipmi-blobs