hiredis: fix paths in pkgconfig conf file

Set PREFIX via EXTRA_OEMAKE instead of exporting it in do_install_prepend():
than ensuring the correct prefix gets into hiredis.pc, which is generated by
upstream makefile at do_compile() time.

Signed-off-by: Andrea Galbusera <gizero@gmail.com>
Signed-off-by: Armin Kuster <akuster808@gmail.com>
(cherry picked from commit 73ac0e419a)
Signed-off-by: Armin Kuster <akuster808@gmail.com>

meta-oe/recipes-extended/hiredis/hiredis_0.13.1.bb

@@ -12,10 +12,11 @@ S = "${WORKDIR}/git"
 
 inherit autotools-brokensep pkgconfig
 
+EXTRA_OEMAKE = "PREFIX=${prefix}"
+
 # By default INSTALL variable in Makefile is equal to 'cp -a', which preserves
 # ownership and causes host-user-contamination QA issue.
 # And PREFIX defaults to /usr/local.
 do_install_prepend() {
-  export PREFIX=${prefix}
   export INSTALL='cp -r'
 }