Mark functions defined in a header with `inline`

Otherwise we risk ODR violations

PiperOrigin-RevId: 546844187
Change-Id: I1163fd19cb21ad5ba9976932dca2b2cd5c2405bd
diff --git a/common/test/bidirectional_deps/leaf_cc_lib.h b/common/test/bidirectional_deps/leaf_cc_lib.h
index 40c4877..5c58e58 100644
--- a/common/test/bidirectional_deps/leaf_cc_lib.h
+++ b/common/test/bidirectional_deps/leaf_cc_lib.h
@@ -9,8 +9,8 @@
   unsigned char field;
 };
 
-LeafCcType Wrap(unsigned char x) { return LeafCcType{x}; }
+inline LeafCcType Wrap(unsigned char x) { return LeafCcType{x}; }
 
-unsigned char Unwrap(LeafCcType x) { return x.field; }
+inline unsigned char Unwrap(LeafCcType x) { return x.field; }
 
 #endif  // CRUBIT_COMMON_TEST_BIDIRECTIONAL_DEPS_LEAF_CC_LIB_H_