cmd/link: delete oReader.flags

Same information is provided from the fields of the embedded
goobj.Reader, and are accessed through it. Delete the flags field.

Change-Id: I7a4f5dca054e567443d719b2931fceff231d6efc
Reviewed-on: https://go-review.googlesource.com/c/go/+/394216
Trust: Cherry Mui <cherryyz@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>

src/cmd/link/internal/loader/loader.go

@@ -76,7 +76,6 @@ type oReader struct {
 	*goobj.Reader
 	unit         *sym.CompilationUnit
 	version      int // version of static symbol
-	flags        uint32 // read from object file
 	pkgprefix    string
 	syms         []Sym    // Sym's global index, indexed by local index
 	pkg          []uint32 // indices of referenced package by PkgIdx (index into loader.objs array)
@@ -2076,7 +2075,6 @@ func (l *Loader) Preload(localSymVersion int, f *bio.Reader, lib *sym.Library, u
 		Reader:       r,
 		unit:         unit,
 		version:      localSymVersion,
-		flags:        r.Flags(),
 		pkgprefix:    pkgprefix,
 		syms:         make([]Sym, ndef+nhashed64def+nhasheddef+r.NNonpkgdef()+r.NNonpkgref()),
 		ndef:         ndef,