初版适配和修改

README_GCC.md

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+# OriginCar GCC build
+
+This keeps the original Keil project intact and adds an ARM GCC build for the
+STM32F407ZG. It reuses the GCC startup file, linker script, SVD and OpenOCD
+tooling from ../../stm32/stm32f407-gcc-framework.
+
+## Commands
+
+    make -j8                 # debug ELF/HEX/BIN with -O0 -g3
+    make release             # size-optimized release build
+    make flash               # build, program, verify and reset through DAPLink
+    make debug-server        # OpenOCD on localhost:3333
+    make linkscope-info      # print the ELF path and observable globals
+
+The LinkScope symbol file is build/debug/OriginCar.elf. Start OpenOCD with
+make debug-server, then select external OpenOCD in LinkScope and connect to
+localhost:3333. The OpenOCD target accepts four GDB connections so VS Code
+Cortex-Debug and LinkScope can share it.
+
+The Homebrew cross compiler has no newlib, so GCC_COMPAT supplies the small C
+runtime surface used by this legacy project. Its printf supports integer,
+string, character, hexadecimal and pointer formats; floating-point formatting
+is intentionally not included.