Add an alternative method for keyboard discovery to speed up build (#6073)

* Add an alternative method for keyboard discovery to speed up build

* Chain MAKEFLAGS for docker_build.sh

* Slight improvement to number of items sent to sort

* Remove debug line

* Fix line escape

Makefile

@@ -20,7 +20,10 @@ endif
 override SILENT := false
 
 ifndef SUB_IS_SILENT
+ifndef SKIP_GIT
     QMK_VERSION := $(shell git describe --abbrev=0 --tags 2>/dev/null)
+endif
+
 ifneq ($(QMK_VERSION),)
 $(info QMK Firmware $(QMK_VERSION))
 endif
@@ -94,6 +97,7 @@ $(eval $(call NEXT_PATH_ELEMENT))
 # endif
 
 define GET_KEYBOARDS
+ifndef ALT_GET_KEYBOARDS
     All_RULES_MK := $$(patsubst $(ROOT_DIR)/keyboards/%/rules.mk,%,$$(wildcard $(ROOT_DIR)/keyboards/*/rules.mk))
     All_RULES_MK += $$(patsubst $(ROOT_DIR)/keyboards/%/rules.mk,%,$$(wildcard $(ROOT_DIR)/keyboards/*/*/rules.mk))
     All_RULES_MK += $$(patsubst $(ROOT_DIR)/keyboards/%/rules.mk,%,$$(wildcard $(ROOT_DIR)/keyboards/*/*/*/rules.mk))
@@ -105,6 +109,9 @@ define GET_KEYBOARDS
     KEYMAPS_MK += $$(patsubst $(ROOT_DIR)/keyboards/%/rules.mk,%,$$(wildcard $(ROOT_DIR)/keyboards/*/*/*/*/keymaps/*/rules.mk))
 
     KEYBOARDS := $$(sort $$(filter-out $$(KEYMAPS_MK), $$(All_RULES_MK)))
+else
+    KEYBOARDS := $(shell find keyboards/ -type f -iname "rules.mk" | grep -v keymaps | sed 's!keyboards/\(.*\)/rules.mk!\1!' | sort | uniq)
+endif
 endef
 
 $(eval $(call GET_KEYBOARDS))

util/docker_build.sh

@@ -46,5 +46,11 @@ fi
 dir=$(pwd -W 2>/dev/null) || dir=$PWD  # Use Windows path if on Windows
 
 # Run container and build firmware
-docker run --rm -it $usb_args -w /qmk_firmware/ -v "$dir":/qmk_firmware qmkfm/base_container \
+docker run --rm -it $usb_args \
+    -w /qmk_firmware/ \
+	-v "$dir":/qmk_firmware \
+	-e ALT_GET_KEYBOARDS=true \
+	-e SKIP_GIT="$SKIP_GIT" \
+	-e MAKEFLAGS="$MAKEFLAGS" \
+	qmkfm/base_container \
 	make "$keyboard${keymap:+:$keymap}${target:+:$target}"