[build] remove examples/build.zig, incorporate into main build.zig

Removes the second build.zig in the examples directory and incorporates it
into the main build.zig. This gives the zig build system the data needed to
know if the raylib library needs to be rebuilt when running any example.

[rcore] fix: TRACELOG upon successfully changing directory

InitWindow() prints CWD during initialization,
but ChangeDirectory() does not, which is quite confusing when you start
messing with CWD. Now said function should log similar message.

I'm sorry... I did not detect this change was breaking batching... :(

[examples] use logarithmic zoom scaling in 2d camera examples

This compensate for slower zoom speed due to log scaling

Add early return when angles are equal in DrawCircleSector and DrawCircleSectorLine functions.

Prevents unnecessary work and division by zero (when segments=0) in DrawCircleSector/DrawCircleSectorLines when startAngle equals endAngle, matching existing behavior in DrawRing/DrawRingLines.

[rcore] Correctly handle window size on resize in auto-scaled HIGHDPI environment

Converting int to char

Fixes warning: narrowing conversion caused by trying to convert int to unsigned char

[rcore] Use snprintf to prevent buffer overflow in path construction

Guard against DEBUG Redefinition

Undefine DEBUG to avoid external redefinition
warnings/conflicts.  This is probably a common
definition for many external build systems'
debug configurations.

This ensures raylib will not emit
a warning about the DEBUG definition being
redefined in external build systems.

[rcore] sinfl_bsr fix for TCC

* update RGFW to 1.6

* properly handle RGFW_quit events

* fix rcore_desktop_rgfw bugs

* update

* update

* uncomment out

* Reorganize some conditions to fix overlap bugs

* Fix edge case where control point selection outlives mouse down

Previous runner `ubuntu-20.04` is deprecated and being removed soon: https://github.com/actions/runner-images/issues/11101

...so it will always prioritize local version of raylib instead of
system-wide installations, which is a huge problem when testing any
changes done locally to raylib as it might cause silent mismatch issues.
There were only 4 examples affected by this issue which were using
`#include <raylib.h>`. Other examples use proper `#include "raylib.h"`

Fixes: https://github.com/raysan5/raylib/issues/4820

* [rcore] fix crash in InitWindow, due to unchecked result of InitPlatform

Check the result of InitPlatform(), if it isn't 0, report the Error
and return. This prevent crashes and allows for gracefully aborting
or recovering by checking IsWindowReady().

Partially-fixes: https://github.com/raysan5/raylib/issues/4801

* [rcore] style: store the result of InitPlatform() before checking it

Small style change that doesn't impact how the code behaves here.
Variable 'result' is not used anywhere else in this block,
it's just for compliance with Raylib's coding conventions.

Requested in PR: https://github.com/raysan5/raylib/pull/4803#discussion_r1976502788

* [rcore] use LOG_WARNING when InitPlatform() fails

...as this is preferred over LOG_ERROR.

Requested-by: https://github.com/raysan5/raylib/pull/4803#discussion_r1976651724

...returning NULL. This was causing a crash few lines later.

Refs: https://github.com/raysan5/raylib/issues/4801#issuecomment-2691201072
Partially-fixes: https://github.com/raysan5/raylib/issues/4801