Support 512K "RCT6" in BTT SKR Mini (#15890)

buildroot/share/PlatformIO/ldscripts/STM32F103RC_SKR_MINI_512K.ld

@@ -0,0 +1,14 @@
+MEMORY
+{
+  ram (rwx) : ORIGIN = 0x20000000, LENGTH = 48K - 40
+  rom (rx)  : ORIGIN = 0x08007000, LENGTH = 512K - 28K
+}
+
+/* Provide memory region aliases for common.inc */
+REGION_ALIAS("REGION_TEXT", rom);
+REGION_ALIAS("REGION_DATA", ram);
+REGION_ALIAS("REGION_BSS", ram);
+REGION_ALIAS("REGION_RODATA", rom);
+
+/* Let common.inc handle the real work. */
+INCLUDE common.inc

buildroot/share/PlatformIO/scripts/STM32F103RC_SKR_MINI.py

@@ -1,13 +1,18 @@
 import os
 Import("env")
 
-# Relocate firmware from 0x08000000 to 0x08007000
+STM32_FLASH_SIZE = 256
+
 for define in env['CPPDEFINES']:
     if define[0] == "VECT_TAB_ADDR":
         env['CPPDEFINES'].remove(define)
+    if define[0] == "STM32_FLASH_SIZE":
+        STM32_FLASH_SIZE = define[1]
+
+# Relocate firmware from 0x08000000 to 0x08007000
 env['CPPDEFINES'].append(("VECT_TAB_ADDR", "0x08007000"))
 
-custom_ld_script = os.path.abspath("buildroot/share/PlatformIO/ldscripts/STM32F103RC_SKR_MINI.ld")
+custom_ld_script = os.path.abspath("buildroot/share/PlatformIO/ldscripts/STM32F103RC_SKR_MINI_" + str(STM32_FLASH_SIZE) + "K.ld")
 for i, flag in enumerate(env["LINKFLAGS"]):
     if "-Wl,-T" in flag:
         env["LINKFLAGS"][i] = "-Wl,-T" + custom_ld_script