Fix Apline compile error on uninitialized value (#7035)

Similar to

* #6330
* #6311
* #6912
* #5946

This extends the region we ignore the gcc warning in.

The warning:

ninja: job failed: /usr/bin/c++  -I/src/src -I/src/third_party/FP16/include -I/src/third_party/llvm-project/include -I/src -static -DBUILD_LLVM_DWARF -Wall -Werror -Wextra -Wno-unused-parameter -Wno-dangling-pointer -fno-omit-frame-pointer -fno-rtti -Wno-implicit-int-float-conversion -Wno-unknown-warning-option -Wswitch -Wimplicit-fallthrough -Wnon-virtual-dtor -fPIC -fdiagnostics-color=always -O3 -DNDEBUG -UNDEBUG -std=c++17 -MD -MT src/passes/CMakeFiles/passes.dir/Precompute.cpp.o -MF src/passes/CMakeFiles/passes.dir/Precompute.cpp.o.d -o src/passes/CMakeFiles/passes.dir/Precompute.cpp.o -c /src/src/passes/Precompute.cpp
In file included from /src/src/literal.h:27,
                 from /src/src/wasm.h:36,
                 from /src/src/ir/boolean.h:20,
                 from /src/src/ir/bits.h:20,
                 from /src/src/ir/properties.h:20,
                 from /src/src/ir/iteration.h:20,
                 from /src/src/passes/Precompute.cpp:30:
In copy constructor 'wasm::SmallVector<T, N>::SmallVector(const wasm::SmallVector<T, N>&) [with T = wasm::Expression*; long unsigned int N = 10]',
    inlined from 'constexpr std::pair<_T1, _T2>::pair(const _T1&, const _T2&) [with _U1 = wasm::Select* const; _U2 = wasm::SmallVector<wasm::Expression*, 10>; typename std::enable_if<(std::_PCC<true, _T1, _T2>::_ConstructiblePair<_U1, _U2>() && std::_PCC<true, _T1, _T2>::_ImplicitlyConvertiblePair<_U1, _U2>()), bool>::type <anonymous> = true; _T1 = wasm::Select* const; _T2 = wasm::SmallVector<wasm::Expression*, 10>]' at /usr/include/c++/13.2.1/bits/stl_pair.h:559:21,
    inlined from 'T& wasm::InsertOrderedMap<Key, T>::operator[](const Key&) [with Key = wasm::Select*; T = wasm::SmallVector<wasm::Expression*, 10>]' at /src/src/support/insert_ordered.h:112:29,
    inlined from 'void wasm::Precompute::partiallyPrecompute(wasm::Function*)::StackFinder::visitSelect(wasm::Select*)' at /src/src/passes/Precompute.cpp:571:24,
    inlined from 'static void wasm::Walker<SubType, VisitorType>::doVisitSelect(SubType*, wasm::Expression**) [with SubType = wasm::Precompute::partiallyPrecompute(wasm::Function*)::StackFinder; VisitorType = wasm::Visitor<wasm::Precompute::partiallyPrecompute(wasm::Function*)::StackFinder, void>]' at /src/src/wasm-delegations.def:50:1:
/src/src/support/small_vector.h:69:35: error: '<unnamed>.wasm::SmallVector<wasm::Expression*, 10>::fixed' may be used uninitialized [-Werror=maybe-uninitialized]
   69 |     : usedFixed(other.usedFixed), fixed(other.fixed), flexible(other.flexible) {
      |                                   ^~~~~~~~~~~~~~~~~~
In file included from /src/src/passes/Precompute.cpp:37:
/src/src/support/insert_ordered.h: In static member function 'static void wasm::Walker<SubType, VisitorType>::doVisitSelect(SubType*, wasm::Expression**) [with SubType = wasm::Precompute::partiallyPrecompute(wasm::Function*)::StackFinder; VisitorType = wasm::Visitor<wasm::Precompute::partiallyPrecompute(wasm::Function*)::StackFinder, void>]':
/src/src/support/insert_ordered.h:112:29: note: '<anonymous>' declared here
  112 |     std::pair<const Key, T> kv = {k, {}};
      |                             ^~

src/support/small_vector.h

@@ -53,14 +53,6 @@ template<typename T, size_t N> class SmallVector {
   // flexible additional storage
   std::vector<T> flexible;
 
-#if defined(__aarch64__)
-#pragma GCC diagnostic pop
-#endif
-
-#if defined(__riscv) && __riscv_xlen == 64
-#pragma GCC diagnostic pop
-#endif
-
 public:
   using value_type = T;
 
@@ -286,6 +278,14 @@ struct ZeroInitSmallVector : public SmallVector<T, N> {
   }
 };
 
+#if defined(__aarch64__)
+#pragma GCC diagnostic pop
+#endif
+
+#if defined(__riscv) && __riscv_xlen == 64
+#pragma GCC diagnostic pop
+#endif
+
 } // namespace wasm
 
 #endif // wasm_support_small_vector_h