Add pkgconfig

Generate pkgconfig for phosphor-ipmi-blobs so that the library can be
found by Meson.

When used as a dependency, phosphor-ipmi-blobs provides only a header
file and no libraries to link against, so the pkgconfig file has no
linker flags.

Tested: added phosphor-ipmi-blobs as a dependency in
phosphor-health-monitor's meson.build file and built successfully.

signed-off-by: Sui Chen <suichen@google.com>
Change-Id: I126c66dbd65ddbd99f921297d813e7a0f9981f22
diff --git a/configure.ac b/configure.ac
index 0b46133..5392c6c 100644
--- a/configure.ac
+++ b/configure.ac
@@ -170,6 +170,9 @@
 AS_IF([test "x$BLOB_LIB_PATH" == "x"], [BLOB_LIB_PATH="/usr/lib/blob-ipmid"])
 AC_DEFINE_UNQUOTED([BLOB_LIB_PATH], ["$BLOB_LIB_PATH"], [The file path to search for libraries.])
 
+AC_CONFIG_FILES([phosphor-ipmi-blobs.pc])
+PKG_INSTALLDIR
+
 # Create configured output
 AC_CONFIG_FILES([Makefile test/Makefile])
 AC_OUTPUT