Fix TLSDESC relocation

Although we do not support TLSDESC on any target on which
ctx.tls_begin != ctx.dtp_addr, my understanding is that the origin
of the TLSDESC base relocation is tls_begin.

elf/output-chunks.cc

@@ -1245,7 +1245,7 @@ static std::vector<GotEntry<E>> get_got_entries(Context<E> &ctx) {
       if (sym->is_imported)
         add({idx, 0, E::R_TLSDESC, sym});
       else
-        add({idx, sym->get_addr(ctx) - ctx.dtp_addr, E::R_TLSDESC});
+        add({idx, sym->get_addr(ctx) - ctx.tls_begin, E::R_TLSDESC});
     }
   }
 

test/elf/tlsdesc.sh

@@ -11,43 +11,45 @@ fi
 
 cat <<EOF | $GCC -fPIC -mtls-dialect=$dialect -c -o $t/a.o -xc -
 extern _Thread_local int foo;
+_Thread_local int bar = 3;
 
 int get_foo() {
   return foo;
 }
 
-static _Thread_local int bar = 5;
+static _Thread_local int baz = 5;
 
-int get_bar() {
-  return bar;
+int get_baz() {
+  return baz;
 }
 EOF
 
 cat <<EOF | $GCC -fPIC -mtls-dialect=$dialect -c -o $t/b.o -xc -
 #include <stdio.h>
 
 _Thread_local int foo;
+extern _Thread_local int bar;
 
 int get_foo();
-int get_bar();
+int get_baz();
 
 int main() {
   foo = 42;
-  printf("%d %d\n", get_foo(), get_bar());
+  printf("%d %d %d\n", get_foo(), bar, get_baz());
   return 0;
 }
 EOF
 
 $CC -B. -o $t/exe1 $t/a.o $t/b.o
-$QEMU $t/exe1 | grep -q '42 5'
+$QEMU $t/exe1 | grep -q '42 3 5'
 
 $CC -B. -o $t/exe2 $t/a.o $t/b.o -Wl,-no-relax
-$QEMU $t/exe2 | grep -q '42 5'
+$QEMU $t/exe2 | grep -q '42 3 5'
 
 $CC -B. -shared -o $t/c.so $t/a.o
 $CC -B. -o $t/exe3 $t/b.o $t/c.so
-$QEMU $t/exe3 | grep -q '42 5'
+$QEMU $t/exe3 | grep -q '42 3 5'
 
 $CC -B. -shared -o $t/c.so $t/a.o -Wl,-no-relax
 $CC -B. -o $t/exe4 $t/b.o $t/c.so -Wl,-no-relax
-$QEMU $t/exe4 | grep -q '42 5'
+$QEMU $t/exe4 | grep -q '42 3 5'