[WebAssembly] fix bug in finding .tdata segment

[quantum]

Summary

Fix bug in wasm-ld's Writer::createInitTLSFunction that only finds .tdata if it's the first section.

[sbc100]

Maybe add a test for this?

[quantum]

Change test to put non-TLS variables first

lld/test/wasm/tls.ll

 ; RUN: llc -mattr=+bulk-memory -filetype=obj %s -o %t.o
 
 target triple = "wasm32-unknown-unknown"
 
-@tls1 = thread_local(localexec) global i32 1, align 4
 @no_tls = global i32 0, align 4
+@tls1 = thread_local(localexec) global i32 1, align 4
 @tls2 = thread_local(localexec) global i32 1, align 4
 
 define i32* @tls1_addr() {
   ret i32* @tls1
 }
 
 define i32* @tls2_addr() {
   ret i32* @tls2

 
 ; CHECK:      - Type:            CODE
 ; CHECK-NEXT:   Functions:
 ; CHECK-NEXT:     - Index:           0
 ; CHECK-NEXT:       Locals:          []
 ; CHECK-NEXT:       Body:            0B
 ; CHECK-NEXT:     - Index:           1
 ; CHECK-NEXT:       Locals:          []
-; CHECK-NEXT:       Body:            20002401200041004108FC0800000B
+; CHECK-NEXT:       Body:            20002401200041004108FC0801000B
 
 ; Expected body of __wasm_init_tls:
 ;   local.get 0
 ;   global.set  1
 ;   local.get 0
 ;   i32.const 0
 ;   i32.const 8
-;   memory.init 0, 0
+;   memory.init 1, 0
 ;   end
 
 ; CHECK-NEXT:     - Index:           2
 ; CHECK-NEXT:       Locals:          []
 ; CHECK-NEXT:       Body:            2381808080004180808080006A0B
 
 ; Expected body of tls1_addr:
 ;   global.get 1

lld/wasm/Writer.cpp

if (!WasmSym::initTLS->isLive())
     return;
 
   std::string bodyContent;
   {
     raw_string_ostream os(bodyContent);
 
     OutputSegment *tlsSeg = nullptr;
     for (auto *seg : segments) {
-      if (seg->name == ".tdata")
+      if (seg->name == ".tdata") {
         tlsSeg = seg;
         break;
       }
+    }
 
     writeUleb128(os, 0, "num locals");
     if (tlsSeg) {
       writeU8(os, WASM_OPCODE_LOCAL_GET, "local.get");
       writeUleb128(os, 0, "local index");
 
       writeU8(os, WASM_OPCODE_GLOBAL_SET, "global.set");
       writeUleb128(os, WasmSym::tlsBase->getGlobalIndex(), "global index");