build: Add .clang for tab-completions

Signed-off-by: Rahix <rahix@rahix.de>

.clang

+flags = -DBOARD_CARD10=1 -D_FILE_OFFSET_BITS=64 -DTARGET=32665 -DTARGET_REV=0x4131 -Ihw-tests/bmatest -Ihw-tests/bmetest -Ihw-tests/ecgtest -Ihw-tests/hello-freertos -Ihw-tests/hello-freertos/./ -Ihw-tests/hello-world -Ihw-tests/imutest -Ihw-tests/ips -Ilib/./card10/./ -Ilib/card10 -Ilib/./gfx/./ -Ilib/gfx -Ilib/./gfx/./Fonts/ -Ilib/./gfx/./GUI_DEV/ -Ilib/./gfx/./LCD/ -Ilib/sdk/Libraries/Boards/card10 -Ilib/./sdk/./Libraries/Boards/card10/../Include/ -Ilib/./sdk/./Libraries/Boards/card10/./Include/ -Ilib/sdk/Libraries/CMSIS/Device/Maxim/MAX32665 -Ilib/./sdk/./Libraries/FreeRTOS/../FreeRTOS-Plus/Source/FreeRTOS-Plus-CLI/ -Ilib/./sdk/./Libraries/FreeRTOS/./Source/include/ -Ilib/./sdk/./Libraries/FreeRTOS/./Source/portable/GCC/ARM_CM4F/ -Ilib/sdk/Libraries/MAX32665PeriphDriver -Ilib/./sdk/./Libraries/MAX32665PeriphDriver/../CMSIS/Device/Maxim/MAX32665/Include/ -Ilib/./sdk/./Libraries/MAX32665PeriphDriver/../CMSIS/Include/ -Ilib/./sdk/./Libraries/MAX32665PeriphDriver/Include/ -Ilib/vendor/Bosch/BHy1 -Ilib/./vendor/Bosch/BHy1/../../../card10/ -Ilib/./vendor/Bosch/BHy1/./driver/inc/ -Ilib/./vendor/Bosch/BHy1/./examples/firmware/ -Ilib/./vendor/Bosch/BMA400/./ -Ilib/vendor/Bosch/BMA400 -Ilib/./vendor/Bosch/BME680/./ -Ilib/vendor/Bosch/BME680 -Ilib/./vendor/Maxim/MAX77650/./ -Ilib/vendor/Maxim/MAX77650