default to skia branch for commit hash in cache helper

Diffs=
dcbe806b0 default to skia branch for commit hash in cache helper (#6432)

Co-authored-by: hernan <hernan@rive.app>

.rive_head

diff --git a/.rive_head b/.rive_head
index 2e9e314..8446bd5 100644
--- a/.rive_head
+++ b/.rive_head
@@ -1 +1 @@
-d67aeac4d7643cdb60f7d22c9b2c0005e7838ed9
+dcbe806b0485977a4c968e93eefcc7e6e01a4460

skia/dependencies/cache_helper.sh

diff --git a/skia/dependencies/cache_helper.sh b/skia/dependencies/cache_helper.sh
index 18f668c..f7e7026 100755
--- a/skia/dependencies/cache_helper.sh
+++ b/skia/dependencies/cache_helper.sh
@@ -8,6 +8,7 @@
 SKIA_DIR_NAME="${SKIA_DIR_NAME:=skia}"
 SKIA_REPO=${SKIA_REPO:-https://github.com/rive-app/skia}
 SKIA_BRANCH=${SKIA_BRANCH:-rive}
+SKIA_COMMIT=${SKIA_COMMIT}
 COMPILE_TARGET="${COMPILE_TARGET:-$(uname -s)_$(uname -m)}"
 CACHE_NAME="${CACHE_NAME:=skia}"
 OUTPUT_CACHE="${OUTPUT_CACHE:=out}"