build: Use only one Makefile for apps

- Use one common Makefile for all test device apps.
- Use a single copy of syscall.[Sh].
- Update docs for building.

hw/application_fpga/apps/defaultapp/Makefile

@@ -1,73 +0,0 @@
-P := $(shell dirname $(realpath $(lastword $(MAKEFILE_LIST))))
-LIBDIR ?= ../../tkey-libs
-OBJCOPY ?= llvm-objcopy
-CC = clang
-CFLAGS = \
-	-target riscv32-unknown-none-elf \
-	-march=rv32iczmmul \
-	-mabi=ilp32 \
-	-mcmodel=medany \
-	-static \
-	-std=gnu99 \
-	-Os \
-	-ffast-math \
-	-fno-common \
-	-fno-builtin-printf \
-	-fno-builtin-putchar \
-	-fno-builtin-memcpy \
-	-nostdlib \
-	-mno-relax \
-	-Wall \
-	-Wpedantic \
-	-Wno-language-extension-token \
-	-Werror \
-	-flto \
-	-g \
-	-I $(LIBDIR)/include \
-	-I $(LIBDIR)
-
-AS = clang
-
-ASFLAGS = \
-	-target riscv32-unknown-none-elf \
-	-march=rv32iczmmul \
-	-mabi=ilp32 \
-	-mno-relax
-
-LDFLAGS = \
-	-T $(LIBDIR)/app.lds \
-	-L $(LIBDIR) -lcrt0 -lcommon -lmonocypher -lblake2s
-
-.PHONY: all
-all: defaultapp.bin
-
-# Turn elf into bin for device
-%.bin: %.elf
-	$(OBJCOPY) --input-target=elf32-littleriscv --output-target=binary $^ $@
-	chmod a-x $@
-
-.PHONY: tkey-libs
-tkey-libs:
-	make -C $(LIBDIR)
-
-DEFAULTAPP_FMTFILES = *.[ch]
-
-DEFAULTAPP_OBJS = \
-	$(P)/main.o \
-	../testapp/syscall.o \
-
-defaultapp.elf: tkey-libs $(DEFAULTAPP_OBJS)
-	$(CC) $(CFLAGS) $(DEFAULTAPP_OBJS) $(LDFLAGS) -o $@
-
-.PHONY: fmt
-fmt:
-	clang-format --dry-run --ferror-limit=0 $(DEFAULTAPP_FMTFILES)
-	clang-format --verbose -i $(DEFAULT_FMTFILES)
-
-.PHONY: checkfmt
-checkfmt:
-	clang-format --dry-run --ferror-limit=0 --Werror $(DEFAULT_FMTFILES)
-
-.PHONY: clean
-clean:
-	rm -f defaultapp.* $(DEFAULTAPP_OBJS)

hw/application_fpga/apps/defaultapp/main.c

@@ -1,13 +1,12 @@
 // Copyright (C) 2025 - Tillitis AB
 // SPDX-License-Identifier: GPL-2.0-only
 
+#include <fw/tk1/reset.h>
+#include <fw/tk1/syscall_num.h>
+#include <syscall.h>
 #include <tkey/debug.h>
 #include <tkey/led.h>
 
-#include "../testapp/syscall.h"
-#include "../tk1/reset.h"
-#include "../tk1/syscall_num.h"
-
 int main(void)
 {
 	struct reset rst = {0};