Set IS_GLINUX in Kokoro builds

- Well, it's not actually glinux, but all the cached files are there, so
lets lie about that.

Change-Id: I9e68eb847665409843e6cac3abc85eccf91dca5d
diff --git a/kokoro/continuous.sh b/kokoro/continuous.sh
index ecc1e45..b197508 100644
--- a/kokoro/continuous.sh
+++ b/kokoro/continuous.sh
@@ -12,6 +12,7 @@
 source build/setup.sh
 popd
 
+export IS_GLINUX=true
 export TARBALL_FETCH_ROOT_DIRECTORY=${KOKORO_GFILE_DIR}
 export PREBUILT_MODULES_ROOT=${KOKORO_GFILE_DIR}
 export PREBUILT_DOCKER_ROOT=${KOKORO_GFILE_DIR}
diff --git a/kokoro/release.sh b/kokoro/release.sh
index 8a78217..291bc40 100644
--- a/kokoro/release.sh
+++ b/kokoro/release.sh
@@ -11,6 +11,7 @@
 source build/setup.sh
 popd
 
+export IS_GLINUX=true
 export TARBALL_FETCH_ROOT_DIRECTORY=${KOKORO_GFILE_DIR}
 export PREBUILT_MODULES_ROOT=${KOKORO_GFILE_DIR}
 export PREBUILT_DOCKER_ROOT=${KOKORO_GFILE_DIR}
diff --git a/kokoro/rootfs.sh b/kokoro/rootfs.sh
index dacfbb3..61d65e0 100644
--- a/kokoro/rootfs.sh
+++ b/kokoro/rootfs.sh
@@ -7,6 +7,7 @@
 source build/setup.sh
 popd
 
+export IS_GLINUX=true
 export ROOTFS_FETCH_TARBALL=false
 export FETCH_PACKAGES=false
 export PREBUILT_DOCKER_ROOT=$KOKORO_GFILE_DIR