[build] add SKIP_BUILD_HOOK support for curl (#15923)

#### Why I did it
To support SKIP_BUILD_HOOK for curl command so the targets downloaded by curl (SONIC_ONLINE_DEBS, SONIC_ONLINE_FILES) can utilize it.

##### Work item tracking
- Microsoft ADO **(number only)**:

#### How I did it
Add a logic to invoke a real command instead of a `download_packages()` (the same way it's done for wget)

#### How to verify it
Add an online target (with URL attribute).
Add the "SKIP_VERSION=y" to this target.
Check that download_packages is not invoked.

src/sonic-build-hooks/hooks/curl

@@ -3,4 +3,9 @@
 . /usr/local/share/buildinfo/scripts/buildinfo_base.sh
 [ -z $REAL_COMMAND ] && REAL_COMMAND=/usr/bin/curl
 
+if [ "$SKIP_BUILD_HOOK" == y ]; then
+    $REAL_COMMAND "$@"
+    exit $?
+fi
+
 REAL_COMMAND=$REAL_COMMAND download_packages "$@"