Make sure to import versioned symbols

Undefined versioned symbols are handled specially; they are resolved
at the very end of name resolution stage. When they are resolved, we
need to make sure that they are marked as imported symbols.

Fixes rui314#1057

elf/passes.cc

@@ -1262,6 +1262,7 @@ void claim_unresolved_symbols(Context<E> &ctx) {
         Symbol<E> *sym2 = get_symbol(ctx, name);
         if (sym2->file && sym2->file->is_dso && sym2->get_version() == ver) {
           file->symbols[i] = sym2;
+          sym2->is_imported = true;
           continue;
         }
       }

test/elf/versioned-undef.sh

@@ -9,10 +9,12 @@ cat <<EOF | $CC -fPIC -c -o $t/a.o -xc -
 int foo1() { return 1; }
 int foo2() { return 2; }
 int foo3() { return 3; }
+int bar3() { return 4; }
 
 __asm__(".symver foo1, foo@VER1");
 __asm__(".symver foo2, foo@VER2");
 __asm__(".symver foo3, foo@@VER3");
+__asm__(".symver bar3, bar@@VER3");
 EOF
 
 echo 'VER1 { local: *; }; VER2 { local: *; }; VER3 { local: *; };' > $t/b.ver
@@ -25,15 +27,17 @@ int foo1();
 int foo2();
 int foo3();
 int foo();
+int bar();
 
 __asm__(".symver foo1, foo@VER1");
 __asm__(".symver foo2, foo@VER2");
 __asm__(".symver foo3, foo@VER3");
+__asm__(".symver bar, bar@VER3");
 
 int main() {
-  printf("%d %d %d %d\n", foo1(), foo2(), foo3(), foo());
+  printf("%d %d %d %d %d\n", foo1(), foo2(), foo3(), foo(), bar());
 }
 EOF
 
 $CC -B. -o $t/exe $t/d.o $t/c.so
-$QEMU $t/exe | grep -q '^1 2 3 3$'
+$QEMU $t/exe | grep -q '^1 2 3 3 4$'