Fix for redundant break statements in nested scopes.

[copybara-service]

Fix for redundant break statements in nested scopes.

Generated by Gemini. Its explanation:

✦ The PipelinedLoopOuterExit test case fails when the break on line 10929 of the test file is present because of a bug in xls/contrib/xlscc/translator.cc where
relative_break_condition was being overwritten by subsequent break statements instead of being accumulated.

Root Cause Analysis
In translator.cc, within the GenerateIR_Stmt function, the handling for clang::BreakStmt and clang::ContinueStmt used simple assignment (=) for relative_break_condition and
relative_continue_condition.

1 // Original buggy code in translator.cc
2 context().relative_break_condition = context().relative_condition_bval(loc);

When a loop body contains multiple break statements, such as:

1 if (x > 10) {
2 if (x == 55) {
3 exit_function = true;
4 break; // Break 1
5 }
6 break; // Break 2
7 }
The translator processes both break statements. When x == 55, Break 1 correctly sets the relative_break_condition. However, the translator continues to process Break 2. Although Break 2 is
logically unreachable in C++ when Break 1 is taken, the translator still evaluates it with its current relative_condition. Because Break 1 calls and_condition(0) to make the rest of the
block a no-op, the relative_condition for Break 2 becomes 0. The assignment relative_break_condition = 0 then overwrites the valid break condition from Break 1, causing the generated IR to
lose the signal to exit the loop.

Fix
The fix involves using or_condition_util to OR the new break/continue condition with any existing ones, ensuring that all possible exit paths are preserved.

1 // Fixed code in translator.cc
2 context().or_condition_util(context().relative_condition_bval(loc),
3 context().relative_break_condition, loc);

This ensures that if any break in the current context is triggered, the relative_break_condition remains true. I have applied this fix to both BreakStmt (for both for and switch bodies)
and ContinueStmt in translator.cc.