[clang] assertion failure llvm::CondBrInst::AssertOK with ubsan enabled

The following code:

```c
typedef short int si8 __attribute__((ext_vector_type(8)));
typedef unsigned int u4 __attribute__((ext_vector_type(4)));
void test_builtin_elementwise_clzg(si8 vs1, si8 vs2, u4 vu1,
char ci) {
vs1 = __builtin_elementwise_clzg(vs1);
}
```

Resulted in this output:
```
clang: /home/fuzz/WorkSpace/fusion-fuzz/projects/clang/llvm-project/llvm/lib/IR/Instructions.cpp:1232: void llvm::CondBrInst::AssertOK(): Assertion `getCondition()->getType()->isIntegerTy(1) && "May only branch on boolean predicates!"' failed.
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace and dumped files.
Stack dump:
0. Program arguments: /home/fuzz/WorkSpace/fusion-fuzz/projects/clang/llvm-clang-install/bin/clang -S -o /dev/null -Oz -std=c99 -fsanitize=undefined -g /tmp/test.c
1. parser at end of file
2. /tmp/test.c:3:6: LLVM IR generation of declaration 'test_builtin_elementwise_clzg'
3. /tmp/test.c:3:6: Generating code for declaration 'test_builtin_elementwise_clzg'
#0 0x0000563187d983e7 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/home/fuzz/WorkSpace/fusion-fuzz/projects/clang/llvm-clang-install/bin/clang+0x24923e7)
#1 0x0000563187d95dc4 llvm::sys::CleanupOnSignal(unsigned long) (/home/fuzz/WorkSpace/fusion-fuzz/projects/clang/llvm-clang-install/bin/clang+0x248fdc4)
#2 0x0000563187cd4218 CrashRecoverySignalHandler(int) CrashRecoveryContext.cpp:0:0
#3 0x00007ff6d9063970 (/usr/lib/x86_64-linux-gnu/libc.so.6+0x40970)
#4 0x00007ff6d90ba1dc (/usr/lib/x86_64-linux-gnu/libc.so.6+0x971dc)
#5 0x00007ff6d9063842 raise (/usr/lib/x86_64-linux-gnu/libc.so.6+0x40842)
#6 0x00007ff6d904b4b2 abort (/usr/lib/x86_64-linux-gnu/libc.so.6+0x284b2)
#7 0x00007ff6d904b424 __assert_perror_fail (/usr/lib/x86_64-linux-gnu/libc.so.6+0x28424)
#8 0x0000563186187723 (/home/fuzz/WorkSpace/fusion-fuzz/projects/clang/llvm-clang-install/bin/clang+0x881723)
#9 0x000056318808735c clang::CodeGen::CodeGenFunction::EmitCheck(llvm::ArrayRef>, SanitizerHandler, llvm::ArrayRef, llvm::ArrayRef, clang::CodeGen::TrapReason const*) (/home/fuzz/WorkSpace/fusion-fuzz/projects/clang/llvm-clang-install/bin/clang+0x278135c)
#10 0x000056318851c8cc clang::CodeGen::CodeGenFunction::EmitCheckedArgForBuiltin(clang::Expr const*, clang::CodeGen::CodeGenFunction::BuiltinCheckKind) (/home/fuzz/WorkSpace/fusion-fuzz/projects/clang/llvm-clang-install/bin/clang+0x2c168cc)
#11 0x000056318852a93a clang::CodeGen::CodeGenFunction::EmitBuiltinExpr(clang::GlobalDecl, unsigned int, clang::CallExpr const*, clang::CodeGen::ReturnValueSlot) (/home/fuzz/WorkSpace/fusion-fuzz/projects/clang/llvm-clang-install/bin/clang+0x2c2493a)
#12 0x00005631880a93e6 clang::CodeGen::CodeGenFunction::EmitCallExpr(clang::CallExpr const*, clang::CodeGen::ReturnValueSlot, llvm::CallBase**) (/home/fuzz/WorkSpace/fusion-fuzz/projects/clang/llvm-clang-install/bin/clang+0x27a33e6)
#13 0x00005631881140cd (anonymous namespace)::ScalarExprEmitter::VisitCallExpr(clang::CallExpr const*) CGExprScalar.cpp:0:0
#14 0x0000563188108d57 (anonymous namespace)::ScalarExprEmitter::Visit(clang::Expr*) CGExprScalar.cpp:0:0
#15 0x000056318811457f (anonymous namespace)::ScalarExprEmitter::VisitBinAssign(clang::BinaryOperator const*) CGExprScalar.cpp:0:0
#16 0x000056318810d97f clang::CodeGen::CodeGenFunction::EmitScalarExpr(clang::Expr const*, bool) (/home/fuzz/WorkSpace/fusion-fuzz/projects/clang/llvm-clang-install/bin/clang+0x280797f)
#17 0x000056318807fb3f clang::CodeGen::CodeGenFunction::EmitAnyExpr(clang::Expr const*, clang::CodeGen::AggValueSlot, bool) (/home/fuzz/WorkSpace/fusion-fuzz/projects/clang/llvm-clang-install/bin/clang+0x2779b3f)
#18 0x00005631880a3b1b clang::CodeGen::CodeGenFunction::EmitIgnoredExpr(clang::Expr const*) (/home/fuzz/WorkSpace/fusion-fuzz/projects/clang/llvm-clang-install/bin/clang+0x279db1b)
#19 0x0000563188230add clang::CodeGen::CodeGenFunction::EmitStmt(clang::Stmt const*, llvm::ArrayRef) (/home/fuzz/WorkSpace/fusion-fuzz/projects/clang/llvm-clang-install/bin/clang+0x292aadd)
#20 0x00005631882388e3 clang::CodeGen::CodeGenFunction::EmitCompoundStmtWithoutScope(clang::CompoundStmt const&, bool, clang::CodeGen::AggValueSlot) (/home/fuzz/WorkSpace/fusion-fuzz/projects/clang/llvm-clang-install/bin/clang+0x29328e3)
#21 0x000056318829a637 clang::CodeGen::CodeGenFunction::EmitFunctionBody(clang::Stmt const*) (/home/fuzz/WorkSpace/fusion-fuzz/projects/clang/llvm-clang-install/bin/clang+0x2994637)
#22 0x00005631882af694 clang::CodeGen::CodeGenFunction::GenerateCode(clang::GlobalDecl, llvm::Function*, clang::CodeGen::CGFunctionInfo const&) (/home/fuzz/WorkSpace/fusion-fuzz/projects/clang/llvm-clang-install/bin/clang+0x29a9694)
#23 0x000056318830a599 clang::CodeGen::CodeGenModule::EmitGlobalFunctionDefinition(clang::GlobalDecl, llvm::GlobalValue*) (/home/fuzz/WorkSpace/fusion-fuzz/projects/clang/llvm-clang-install/bin/clang+0x2a04599)
#24 0x00005631883043b5 clang::CodeGen::CodeGenModule::EmitGlobalDefinition(clang::GlobalDecl, llvm::GlobalValue*) (/home/fuzz/WorkSpace/fusion-fuzz/projects/clang/llvm-clang-install/bin/clang+0x29fe3b5)
#25 0x0000563188305088 clang::CodeGen::CodeGenModule::EmitGlobal(clang::GlobalDecl) (/home/fuzz/WorkSpace/fusion-fuzz/projects/clang/llvm-clang-install/bin/clang+0x29ff088)
#26 0x000056318830fcf1 clang::CodeGen::CodeGenModule::EmitTopLevelDecl(clang::Decl*) (.part.0) CodeGenModule.cpp:0:0
#27 0x00005631886664b0 (anonymous namespace)::CodeGeneratorImpl::HandleTopLevelDecl(clang::DeclGroupRef) ModuleBuilder.cpp:0:0
#28 0x0000563188656afa clang::BackendConsumer::HandleTopLevelDecl(clang::DeclGroupRef) (/home/fuzz/WorkSpace/fusion-fuzz/projects/clang/llvm-clang-install/bin/clang+0x2d50afa)
#29 0x000056318a3eb523 clang::ParseAST(clang::Sema&, bool, bool) (/home/fuzz/WorkSpace/fusion-fuzz/projects/clang/llvm-clang-install/bin/clang+0x4ae5523)
#30 0x00005631889e265a clang::FrontendAction::Execute() (/home/fuzz/WorkSpace/fusion-fuzz/projects/clang/llvm-clang-install/bin/clang+0x30dc65a)
#31 0x000056318896970a clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) (/home/fuzz/WorkSpace/fusion-fuzz/projects/clang/llvm-clang-install/bin/clang+0x306370a)
#32 0x0000563188ab071a clang::ExecuteCompilerInvocation(clang::CompilerInstance*) (/home/fuzz/WorkSpace/fusion-fuzz/projects/clang/llvm-clang-install/bin/clang+0x31aa71a)
#33 0x000056318686e8f3 cc1_main(llvm::ArrayRef, char const*, void*) (/home/fuzz/WorkSpace/fusion-fuzz/projects/clang/llvm-clang-install/bin/clang+0xf688f3)
#34 0x00005631868662b8 ExecuteCC1Tool(llvm::SmallVectorImpl&, llvm::ToolContext const&, llvm::IntrusiveRefCntPtr) driver.cpp:0:0
#35 0x000056318686648a int llvm::function_ref&)>::callback_fn&)>(long, llvm::SmallVectorImpl&) driver.cpp:0:0
#36 0x00005631886dc529 void llvm::function_ref::callback_fn>, std::__cxx11::basic_string, std::allocator>*, bool*) const::'lambda'()>(long) Job.cpp:0:0
#37 0x0000563187cd45d1 llvm::CrashRecoveryContext::RunSafely(llvm::function_ref) (/home/fuzz/WorkSpace/fusion-fuzz/projects/clang/llvm-clang-install/bin/clang+0x23ce5d1)
#38 0x00005631886dd99b clang::driver::CC1Command::Execute(llvm::ArrayRef>, std::__cxx11::basic_string, std::allocator>*, bool*) const (.part.0) Job.cpp:0:0
#39 0x0000563188690ef8 clang::driver::Compilation::ExecuteCommand(clang::driver::Command const&, clang::driver::Command const*&, bool) const (/home/fuzz/WorkSpace/fusion-fuzz/projects/clang/llvm-clang-install/bin/clang+0x2d8aef8)
#40 0x000056318869618d clang::driver::Compilation::ExecuteJobs(clang::driver::JobList const&, llvm::SmallVectorImpl>&, bool) const (/home/fuzz/WorkSpace/fusion-fuzz/projects/clang/llvm-clang-install/bin/clang+0x2d9018d)
#41 0x00005631886a90e5 clang::driver::Driver::ExecuteCompilation(clang::driver::Compilation&, llvm::SmallVectorImpl>&) (/home/fuzz/WorkSpace/fusion-fuzz/projects/clang/llvm-clang-install/bin/clang+0x2da30e5)
#42 0x000056318686b534 clang_main(int, char**, llvm::ToolContext const&) (/home/fuzz/WorkSpace/fusion-fuzz/projects/clang/llvm-clang-install/bin/clang+0xf65534)
#43 0x00005631867b0bc5 main (/home/fuzz/WorkSpace/fusion-fuzz/projects/clang/llvm-clang-install/bin/clang+0xeaabc5)
#44 0x00007ff6d904cf77 (/usr/lib/x86_64-linux-gnu/libc.so.6+0x29f77)
#45 0x00007ff6d904d027 __libc_start_main (/usr/lib/x86_64-linux-gnu/libc.so.6+0x2a027)
#46 0x0000563186865521 _start (/home/fuzz/WorkSpace/fusion-fuzz/projects/clang/llvm-clang-install/bin/clang+0xf5f521)
clang: error: clang frontend command failed due to signal (use -v to see invocation)
clang version 24.0.0git (https://github.com/llvm/llvm-project.git 353729bbe4c53086c9acf3a9d1a4a88a61eec997)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/fuzz/WorkSpace/fusion-fuzz/projects/clang/llvm-clang-install/bin
Build config: +assertions
clang: note: diagnostic msg:
********************

PLEASE ATTACH THE FOLLOWING CRASH REPRODUCER FILES TO THE BUG REPORT:
clang: note: diagnostic msg: /tmp/test-71c6d5.c
clang: note: diagnostic msg: /tmp/test-71c6d5.sh
clang: note: diagnostic msg:

********************
Aborted (core dumped)
```

To reproduce:
```
/home/fuzz/WorkSpace/fusion-fuzz/projects/clang/llvm-clang-install/bin/clang -fsanitize=undefined ./test.c
```

Compiler version:
```
clang version 24.0.0git (https://github.com/llvm/llvm-project.git 353729bbe4c53086c9acf3a9d1a4a88a61eec997)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/fuzz/WorkSpace/fusion-fuzz/projects/clang/llvm-clang-install/bin
Build config: +assertions
```

*This bug was found by [fusion-fuzz](https://github.com/fusion-fuzz/fusion-fuzz)*

Reproduce the C snippet with -fsanitize=undefined, then inspect clang::CodeGen::CodeGenFunction::EmitCheckedArgForBuiltin and EmitBuiltinExpr, where the stack reaches llvm/lib/IR/Instructions.cpp:1232. Trace the __builtin_elementwise_clzg path and verify that the input compiles without the CondBrInst assertion.

Written by the indexing model from the issue text.