Handle "file not found" error in the superclass's errStr().

If a subclass does not override the member function, the superclass's method
takes care of string conversion of "file not found" error. This is a reasonable
default behavior. Subclasses are still able to override to customize error
messages.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@191058 91177308-0d34-0410-b5e6-96231b3b80d8
Remove extraneous parentheses.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@191061 91177308-0d34-0410-b5e6-96231b3b80d8
[PECOFF] Ignore /incremental option.

/incremental is an option to enable incremental linking. We will eventually
want to implement the feature for better performance, but in the meantime,
we want to just ignore the option so that the linker does not output unknown
option error when it sees /incremental option.

git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@191063 91177308-0d34-0410-b5e6-96231b3b80d8