[SYS] esp32-arduino-libs: bump 0.1.7 -> 0.1.8 (restores RISC-V -march) (#2352)

0.1.7 shipped esp32c3 flags with no -march at all, so every ESP32-C2/C3 build
fell back to the compiler default (rv32imafdc) and emitted atomic and
hardware-FP instructions the core does not implement. The firmware panicked
with "Illegal instruction" during C++ static init — on the first
std::shared_ptr refcount, inside the Arduino core's global SPIFFS constructor —
so the board boot-looped before printing a single line of OMG output. That is
issue #2336: esp32c3-dev-c2-ble dev builds boot-loop while 1.8.1 (built on
arduino-esp32 2.x, which passed -march=rv32imc explicitly) is fine.

The flag was lost in packaging, not in the compiler: ESP-IDF >= 5.5.2 moved the
toolchain base flags into @response files and the lib-builder's flag extraction
silently dropped them. The precompiled libs were always correct RV32IMC code.
0.1.8 restores -march across c_flags/cpp_flags/S_flags/ld_flags and
pioarduino-build.py, and fails the lib build if a target's ISA flag ever goes
missing again (theengs/esp32-arduino-lib-builder#9).

Xtensa targets were never affected — each core has its own GCC driver whose
default multilib already matches — but they are rebuilt from the same bundle,
so esp32/esp32s3 want a smoke test alongside the C3.

Bench-verified on an ESP32-C3 rev v0.4: boot-loops on 0.1.7 (30 panics in 20 s,
MTVAL 0x06f7202f), boots and decodes BLE on 0.1.8 with no project-level flags.

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

platformio.ini

@@ -181,7 +181,7 @@ extra_scripts = pre:scripts/add_mlongcalls.py
 [com]
 esp8266_platform = espressif8266@4.2.1
 esp32_platform =  https://github.com/pioarduino/platform-espressif32/releases/download/55.03.39/platform-espressif32.zip
-esp32_platform_packages = framework-arduinoespressif32-libs @ https://github.com/theengs/esp32-arduino-lib-builder/releases/download/0.1.7/esp32-arduino-libs.tar.gz
+esp32_platform_packages = framework-arduinoespressif32-libs @ https://github.com/theengs/esp32-arduino-lib-builder/releases/download/0.1.8/esp32-arduino-libs.tar.gz
 esp32_solo_platform = https://github.com/tasmota/platform-espressif32/releases/download/2023.02.00/platform-espressif32.zip
 atmelavr_platform = atmelavr@3.3.0