Fixed build error blocking Android roll

Change-Id: Ib3dc98192fcfca2af933cc0aa196b3cd47558593
TBR=brianosman@google.com, stani@google.com
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/306942
Reviewed-by: Stan Iliev <stani@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>

src/sksl/ir/SkSLBinaryExpression.h

@@ -19,7 +19,7 @@
 
 namespace SkSL {
 
-static bool check_ref(Expression* expr) {
+static inline bool check_ref(Expression* expr) {
     switch (expr->fKind) {
         case Expression::kExternalValue_Kind:
             return true;