make --dylib mode work on linux

We're looking up skvm_jit where we need to look up _skvm_jit.

Change-Id: Iad00d2a371cbec590ebecc2ead15dc0aab5a1d4b
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/285676
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
diff --git a/src/core/SkVM.cpp b/src/core/SkVM.cpp
index d7aaa72..4925a1b 100644
--- a/src/core/SkVM.cpp
+++ b/src/core/SkVM.cpp
@@ -3521,7 +3521,11 @@
 
             // Load that dynamic library and look up skvm_jit().
             fImpl->dylib = dlopen(path.c_str(), RTLD_NOW|RTLD_LOCAL);
-            fImpl->jit_entry.store(dlsym(fImpl->dylib, "skvm_jit"));
+            void* sym = nullptr;
+            for (const char* name : {"skvm_jit", "_skvm_jit"} ) {
+                if (!sym) { sym = dlsym(fImpl->dylib, name); }
+            }
+            fImpl->jit_entry.store(sym);
         }
     }
 #endif