hardcode "platform = espressif32@6.3.1" for all targets

platformio.ini

@@ -39,7 +39,7 @@ unbuild_flags =
   ${common.core_unbuild_flags}
 
 [espressi32_base]
-platform = espressif32
+platform = espressif32@6.3.1
 framework = arduino
 build_flags = ${common.build_flags}
 build_unflags = ${common.unbuild_flags}
@@ -64,8 +64,7 @@ check_flags =
 ; build for GitHub Actions CI
 ; the Web interface is built seperately
 [env:ci]
-platform = espressif32
-framework = arduino
+extends = espressi32_base
 extra_scripts = scripts/rename_fw.py
 board = esp32dev
 board_build.partitions = esp32_partition_4M.csv
@@ -75,8 +74,8 @@ build_unflags = ${common.unbuild_flags}
 
 ; for github Actions actually standard platform is buggy, use dev-platform
 [env:ci_s3]
+extends = espressi32_base
 platform = https://github.com/platformio/platform-espressif32.git
-framework = arduino
 extra_scripts = scripts/rename_fw.py
 board = lolin_s3
 board_build.f_cpu = 240000000L