feat: build userspace programs with the x86_64-montauk toolchain

Switch all program and library Makefiles from host g++ (or the
bare-metal x86_64-elf compiler) to x86_64-montauk-g++/gcc and drop the
flags the target now owns: -nostdinc + kernel freestanding -isystem
paths, -m64/-march, -fno-PIC, -mno-red-zone, -mcmodel=small, -static,
-Wl,-m,elf_x86_64, -z max-page-size, --build-id=none. Deliberate
policy flags stay (-ffreestanding, per-app SSE, -nostdlib + link.ld).

Program builds now require the montauk toolchain and fail with a
pointer to build-montauk-toolchain.sh; lib/ and libs/ keep the host
fallback since the toolchain script bootstraps libc through it.
Userspace is also now pinned to the cross GCC instead of drifting
with the distro compiler.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

programs/src/dialogs/Makefile

@@ -4,17 +4,17 @@
 MAKEFLAGS += -rR
 .SUFFIXES:
 
-TOOLCHAIN_PREFIX := $(shell cd ../../.. && pwd)/toolchain/local/bin/x86_64-elf-
-ifneq ($(wildcard $(TOOLCHAIN_PREFIX)gcc),)
+TOOLCHAIN_PREFIX := $(shell cd ../../.. && pwd)/toolchain/local/bin/x86_64-montauk-
+ifeq ($(wildcard $(TOOLCHAIN_PREFIX)gcc),)
+    CC = $(error x86_64-montauk toolchain not found. Run ./toolchain/build-montauk-toolchain.sh first)
+    CXX = $(error x86_64-montauk toolchain not found. Run ./toolchain/build-montauk-toolchain.sh first)
+    LD = $(error x86_64-montauk toolchain not found. Run ./toolchain/build-montauk-toolchain.sh first)
+    STRIP = $(error x86_64-montauk toolchain not found. Run ./toolchain/build-montauk-toolchain.sh first)
+else
     CC  := $(TOOLCHAIN_PREFIX)gcc
     CXX := $(TOOLCHAIN_PREFIX)g++
     LD  := $(TOOLCHAIN_PREFIX)ld
     STRIP := $(TOOLCHAIN_PREFIX)strip
-else
-    CC  := gcc
-    CXX := g++
-    LD  := ld
-    STRIP := strip
 endif
 
 PROG_INC := ../../include
@@ -31,7 +31,6 @@ CXXFLAGS := \
     -Wextra \
     -Wno-unused-parameter \
     -Wno-unused-function \
-    -nostdinc \
     -ffreestanding \
     -fno-stack-protector \
     -fno-stack-check \
@@ -41,19 +40,13 @@ CXXFLAGS := \
     -fno-exceptions \
     -ffunction-sections \
     -fdata-sections \
-    -m64 \
-    -march=x86-64 \
     -msse \
     -msse2 \
-    -mno-red-zone \
-    -mcmodel=small \
     -MMD -MP \
     -DGUI_DIALOGS_LIBRARY_BUILD \
     -I $(PROG_INC) \
     -isystem $(PROG_INC)/libc \
-    -I ../../lib/bearssl/inc \
-    -isystem ../../../kernel/freestnd-c-hdrs/x86_64/include \
-    -isystem ../../../kernel/freestnd-cxx-hdrs/x86_64/include
+    -I ../../lib/bearssl/inc
 
 LDFLAGS := \
     -shared \
@@ -62,15 +55,13 @@ LDFLAGS := \
     --hash-style=sysv \
     -u dialogs_run_request \
     -u dialogs_message_box \
-    -m elf_x86_64 \
-    -z max-page-size=0x1000
+    -m elf_x86_64
 
 LIBC_CFLAGS := \
     -std=gnu11 \
     -g -O2 -pipe \
     -Wall \
     -Wno-unused-parameter \
-    -nostdinc \
     -ffreestanding \
     -fno-stack-protector \
     -fno-stack-check \
@@ -78,12 +69,8 @@ LIBC_CFLAGS := \
     -fvisibility=hidden \
     -ffunction-sections \
     -fdata-sections \
-    -m64 \
-    -march=x86-64 \
     -msse \
     -msse2 \
-    -mno-red-zone \
-    -mcmodel=small \
     -isystem $(PROG_INC)/libc \
     -isystem $(GCC_INCLUDE)