SCons: Remove unnecessary $LINK overrides

As of SCons 4.0.1, the default value for $LINK is $SMARTLINK, which itself
is a function that will use $CXX as linker for C++:

https://github.com/SCons/scons/blob/4.0.1/SCons/Tool/link.py#L327-L328
https://github.com/SCons/scons/blob/4.0.1/SCons/Tool/link.py#L54-L76

So we don't need to manually specify the same value as $CXX for $LINK.

platform/linuxbsd/detect.py

@@ -129,7 +129,6 @@ def configure(env):
         if "clang++" not in os.path.basename(env["CXX"]):
             env["CC"] = "clang"
             env["CXX"] = "clang++"
-            env["LINK"] = "clang++"
         env.Append(CPPDEFINES=["TYPED_METHOD_BIND"])
         env.extra_suffix = ".llvm" + env.extra_suffix