build.sh: pull in Ignition COPR for ignition-validate

Since a new one that supports spec v3.0.0 isn't in Fedora proper yet.

Closes: coreos#448

build.sh

@@ -39,12 +39,19 @@ configure_yum_repos() {
     fi
 }
 
+# this matches basearch for the arches we care about
+arch=$(uname -m)
+
 install_rpms() {
     # First, a general update; this is best practice.  We also hit an issue recently
     # where qemu implicitly depended on an updated libusbx but didn't have a versioned
     # requires https://bugzilla.redhat.com/show_bug.cgi?id=1625641
     yum -y distro-sync
 
+    # XXX: just hack this for now until it makes it into Fedora proper or the
+    # continuous repo
+    yum -y install "https://kojipkgs.fedoraproject.org//packages/ignition/2.0.0/alpha.3.git906cf04.fc29/$arch/ignition-validate-2.0.0-alpha.3.git906cf04.fc29.$arch.rpm"
+
     # xargs is part of findutils, which may not be installed
     yum -y install /usr/bin/xargs
 
@@ -103,7 +110,6 @@ _prep_make_and_make_install() {
     fi
 }
 
-arch=$(uname -m)
 release="29"
 # Download url is different for primary and secondary fedora
 # Primary Fedora - https://download.fedoraproject.org/pub/fedora/linux/releases/