fix: duplicate ninja rules for v8 (cross-compiling)

avoids duplicate ninja rules for v8 used in host and target

From: minrk/node@5e533cb
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

Reported in nodejs/node#46690
and nodejs/node#37441

Minor refactoring as recommended by Christian Clauss.

Signed-off-by: Tim Orling <tim.orling@konsulko.com>

pylib/gyp/generator/ninja.py

@@ -42,7 +42,7 @@
     # the start of a string, while $| is used for variables that can appear
     # anywhere in a string.
     "INTERMEDIATE_DIR": "$!INTERMEDIATE_DIR",
-    "SHARED_INTERMEDIATE_DIR": "$!PRODUCT_DIR/gen",
+    "SHARED_INTERMEDIATE_DIR": "$!PRODUCT_DIR/$|OBJ/gen",
     "PRODUCT_DIR": "$!PRODUCT_DIR",
     "CONFIGURATION_NAME": "$|CONFIGURATION_NAME",
     # Special variables that may be used by gyp 'rule' targets.
@@ -285,7 +285,8 @@ def ExpandSpecial(self, path, product_dir=None):
         CONFIGURATION_NAME = "$|CONFIGURATION_NAME"
         path = path.replace(CONFIGURATION_NAME, self.config_name)
 
-        return path
+        obj = "obj" if self.toolset == "target" else f"obj.{self.toolset}"
+        return path.replace("$|OBJ", obj)
 
     def ExpandRuleVariables(self, path, root, dirname, source, ext, name):
         if self.flavor == "win":