LibCore: Add System::getpid

Author: https://github.com/stasoid
Commit: https://github.com/LadybirdBrowser/ladybird/commit/212cea4535d
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/2921

Libraries/LibCore/System.cpp

@@ -999,4 +999,9 @@ ErrorOr<void> set_resource_limits(int resource, rlim_t limit)
     return {};
 }
 
+int getpid()
+{
+    return ::getpid();
+}
+
 }

Libraries/LibCore/System.h

@@ -179,4 +179,6 @@ ErrorOr<rlimit> get_resource_limits(int resource);
 ErrorOr<void> set_resource_limits(int resource, rlim_t limit);
 #endif
 
+int getpid();
+
 }

Libraries/LibCore/SystemWindows.cpp

@@ -184,4 +184,9 @@ ErrorOr<void> munmap(void* address, size_t size)
     return {};
 }
 
+int getpid()
+{
+    return GetCurrentProcessId();
+}
+
 }