{esp32,rp2,stm32}/Makefile: Append board variant to BUILD.

This allows switching between variants without clobbering the build
output.

This work was funded through GitHub Sponsors.

Signed-off-by: Jim Mussared <jim.mussared@gmail.com>

ports/esp32/Makefile

@@ -17,8 +17,13 @@ ifeq ($(wildcard $(BOARD_DIR)/.),)
 $(error Invalid BOARD specified: $(BOARD_DIR))
 endif
 
-# If the build directory is not given, make it reflect the board name.
+# If the build directory is not given, make it reflect the board name (and
+# optionally the board variant).
+ifneq ($(BOARD_VARIANT),)
+BUILD ?= build-$(BOARD)-$(BOARD_VARIANT)
+else
 BUILD ?= build-$(BOARD)
+endif
 
 # Device serial settings.
 PORT ?= /dev/ttyUSB0

ports/rp2/Makefile

@@ -16,8 +16,14 @@ endif
 ifeq ($(wildcard $(BOARD_DIR)/.),)
 $(error Invalid BOARD specified: $(BOARD_DIR))
 endif
- 
+
+# If the build directory is not given, make it reflect the board name (and
+# optionally the board variant).
+ifneq ($(BOARD_VARIANT),)
+BUILD ?= build-$(BOARD)-$(BOARD_VARIANT)
+else
 BUILD ?= build-$(BOARD)
+endif
 
 $(VERBOSE)MAKESILENT = -s
 

ports/stm32/Makefile

@@ -13,8 +13,13 @@ ifeq ($(wildcard $(BOARD_DIR)/.),)
 $(error Invalid BOARD specified: $(BOARD_DIR))
 endif
 
-# If the build directory is not given, make it reflect the board name.
+# If the build directory is not given, make it reflect the board name (and
+# optionally the board variant).
+ifneq ($(BOARD_VARIANT),)
+BUILD ?= build-$(BOARD)-$(BOARD_VARIANT)
+else
 BUILD ?= build-$(BOARD)
+endif
 
 include ../../py/mkenv.mk
 -include mpconfigport.mk