Special-case paths that appear in libs by not prefixing them with -l.

tools/gn/value_extractors.h

Index: tools/gn/value_extractors.h
diff --git a/tools/gn/value_extractors.h b/tools/gn/value_extractors.h
index 2482ba25bf2b3a82e19d6adc29585eb5fe6f67ed..06d64cef676e78d62fdc0c9c1dfa19f963567739 100644
--- a/tools/gn/value_extractors.h
+++ b/tools/gn/value_extractors.h
@@ -9,6 +9,7 @@
 #include <vector>
 
 #include "tools/gn/label_ptr.h"
+#include "tools/gn/lib_file.h"
 #include "tools/gn/unique_vector.h"
 
 class BuildSettings;
@@ -30,6 +31,14 @@ bool ExtractListOfRelativeFiles(const BuildSettings* build_settings,
                                 std::vector<SourceFile>* files,
                                 Err* err);
 
+// Extracts a list of libraries. When they contain a "/" they are treated as
+// source paths and are otherwise treated as plain strings.
+bool ExtractListOfLibs(const BuildSettings* build_settings,
+                       const Value& value,
+                       const SourceDir& current_dir,
+                       std::vector<LibFile>* libs,
+                       Err* err);
+
 // Looks for a list of source directories relative to a given current dir.
 bool ExtractListOfRelativeDirs(const BuildSettings* build_settings,
                                const Value& value,