🔨 Build flag tweaks

Author: thinkyhead

Marlin/src/core/macros.h

@@ -37,11 +37,12 @@
 #define  FORCE_INLINE  __attribute__((always_inline)) inline
 #define NO_INLINE      __attribute__((noinline))
 #define _UNUSED      __attribute__((unused))
-#define __O0         __attribute__((optimize("O0")))
-#define __Os         __attribute__((optimize("Os")))
-#define __O1         __attribute__((optimize("O1")))
-#define __O2         __attribute__((optimize("O2")))
-#define __O3         __attribute__((optimize("O3")))
+#define __O0         __attribute__((optimize("O0")))  // No optimization and less debug info
+#define __Og         __attribute__((optimize("Og")))  // Optimize the debugging experience
+#define __Os         __attribute__((optimize("Os")))  // Optimize for size
+#define __O1         __attribute__((optimize("O1")))  // Try to reduce size and cycles; nothing that takes a lot of time to compile
+#define __O2         __attribute__((optimize("O2")))  // Optimize even more
+#define __O3         __attribute__((optimize("O3")))  // Optimize yet more
 
 #define IS_CONSTEXPR(...) __builtin_constant_p(__VA_ARGS__) // Only valid solution with C++14. Should use std::is_constant_evaluated() in C++20 instead
 

ini/avr.ini

@@ -14,8 +14,8 @@
 #
 [common_avr8]
 platform          = atmelavr@~4.0.1
-build_flags       = ${common.build_flags} -Wl,--relax
-build_src_flags   = -std=gnu++1z
+build_flags       = ${common.build_flags} -std=gnu++1z -Wl,--relax
+build_unflags     = -std=gnu++11
 board_build.f_cpu = 16000000L
 build_src_filter  = ${common.default_src_filter} +<src/HAL/AVR>
 

ini/stm32f1-maple.ini

@@ -326,7 +326,7 @@ extends     = STM32F1_maple
 board       = marlin_malyanM200
 build_flags = ${STM32F1_maple.build_flags}
               -DMCU_STM32F103CB -D__STM32F1__=1 -std=c++1y -DSERIAL_USB -ffunction-sections -fdata-sections
-              -Wl,--gc-sections -DDEBUG_LEVEL=0 -D__MARLIN_FIRMWARE__
+              -Wl,--gc-sections -DDEBUG_LEVEL=0
 lib_ignore  = ${STM32F1_maple.lib_ignore}
               SoftwareSerialM