gn: Add runtime_link_output to tool("solib")

tools/gn/docs/reference.md

 # GN Reference
 
 *This page is automatically generated from* `gn help --markdown all`.
 
 ## **\--args**: Specifies build arguments overrides.
 
 ```
   See "gn help buildargs" for an overview of how build arguments work.
 
   Most operations take a build directory. The build arguments are taken
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         are relative to the build output directory. There must always be
         at least one output file. There can be more than one output (a
         linker might produce a library and an import library, for
         example).
 
         This array just declares to GN what files the tool will
         produce. It is your responsibility to specify the tool command
         that actually produces these files.
 
         If you specify more than one output for shared library links,
-        you should consider setting link_output and depend_output.
-        Otherwise, the first entry in the outputs list should always be
-        the main output which will be linked to.
+        you should consider setting link_output, depend_output, and
+        runtime_link_output. Otherwise, the first entry in the
+        outputs list should always be the main output which will be
+        linked to.
 
         Example for a compiler tool that produces .obj files:
           outputs = [
             "{{source_out_dir}}/{{source_name_part}}.obj"
           ]
 
         Example for a linker tool that produces a .dll and a .lib. The
         use of {{output_extension}} rather than hardcoding ".dll"
         allows the extension of the library to be overridden on a
         target-by-target basis, but in this example, it always
         produces a ".lib" import library:
           outputs = [
             "{{root_out_dir}}/{{target_output_name}}{{output_extension}}",
             "{{root_out_dir}}/{{target_output_name}}.lib",
           ]
 
     link_output  [string with substitutions]
     depend_output  [string with substitutions]
+    runtime_link_output  [string with substitutions]
         Valid for: "solink" only (optional)
 
-        These two files specify which of the outputs from the solink
+        These three files specify which of the outputs from the solink
         tool should be used for linking and dependency tracking. These
         should match entries in the "outputs". If unspecified, the
-        first item in the "outputs" array will be used for both. See
+        first item in the "outputs" array will be used for all. See
         "Separate linking and dependencies for shared libraries"
-        below for more.
+        below for more.  If link_output is set but runtime_link_output
+        is not set, runtime_link_output defaults to link_output.
 
         On Windows, where the tools produce a .dll shared library and
-        a .lib import library, you will want both of these to be the
-        import library. On Linux, if you're not doing the separate
-        linking/dependency optimization, both of these should be the
-        .so output.
+        a .lib import library, you will want the first two to be the
+        import library and the third one to be the .dll file.
+        On Linux, if you're not doing the separate linking/dependency
+        optimization, all of these should be the .so output.
 
     output_prefix  [string]
         Valid for: Linker tools (optional)
 
         Prefix to use for the output name. Defaults to empty. This
         prefix will be prepended to the name of the target (or the
         output_name if one is manually specified for it) if the prefix
         is not already there. The result will show up in the
         {{output_name}} substitution pattern.
 
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 **  -q**: Quiet mode. Don't print output on success.
 **  \--root**: Explicitly specify source root.
 **  \--runtime-deps-list-file**: Save runtime dependencies for targets in file.
 **  \--threads**: Specify number of worker threads.
 **  \--time**: Outputs a summary of how long everything took.
 **  \--tracelog**: Writes a Chrome-compatible trace log to the given file.
 **  -v**: Verbose logging.
 **  \--version**: Prints the GN version number and exits.
 
 ```