Use label name to generate PDB names in GN.

build/toolchain/win/BUILD.gn

Index: build/toolchain/win/BUILD.gn
diff --git a/build/toolchain/win/BUILD.gn b/build/toolchain/win/BUILD.gn
index 97dca966d1085277744ddb366e00e23d2003f7d1..e3100399575941eb81519f51096487f4f217ad78 100644
--- a/build/toolchain/win/BUILD.gn
+++ b/build/toolchain/win/BUILD.gn
@@ -67,7 +67,7 @@ template("msvc_toolchain") {
     tool("cc") {
       rspfile = "{{output}}.rsp"
       precompiled_header_type = "msvc"
-      pdbname = "{{target_out_dir}}/{{target_output_name}}_c.pdb"
+      pdbname = "{{target_out_dir}}/{{label_name}}_c.pdb"
       command = "ninja -t msvc -e $env -- $cl /nologo /showIncludes /FC @$rspfile /c {{source}} /Fo{{output}} /Fd$pdbname"
       depsformat = "msvc"
       description = "CC {{output}}"
@@ -82,7 +82,7 @@ template("msvc_toolchain") {
       precompiled_header_type = "msvc"
 
       # The PDB name needs to be different between C and C++ compiled files.
-      pdbname = "{{target_out_dir}}/{{target_output_name}}_cc.pdb"
+      pdbname = "{{target_out_dir}}/{{label_name}}_cc.pdb"
       command = "ninja -t msvc -e $env -- $cl /nologo /showIncludes /FC @$rspfile /c {{source}} /Fo{{output}} /Fd$pdbname"
       depsformat = "msvc"
       description = "CXX {{output}}"