Add pre-RTOS Dmod_Mutex_New guard via --wrap to fix VFS mounts

The dmosi bridge provides a strong Dmod_Mutex_New that creates a FreeRTOS
mutex using pvPortMalloc+xSemaphoreCreateRecursiveMutex even before the
scheduler starts. Mutex creation succeeds but locking returns -ENOTSUP
pre-RTOS, causing all three dmvfs_mount_fs calls to fail with
"Failed to lock DMVFS mutex". This prevents board modules (dmgpio,
dmclk, dmdevfs) from loading, blocking crash reproduction.

Fix: src/arch/armv7/dmod_mutex.c wraps Dmod_Mutex_New via
-Wl,--wrap=Dmod_Mutex_New. The wrapper returns NULL when
!dmosi_is_started() so dmvfs falls back to Dmod_EnterCritical/
ExitCritical (interrupt-disable critical sections). After
vTaskStartScheduler the wrapper forwards to the real implementation.

src/arch/armv7/CMakeLists.txt: add dmod_mutex.c to dmboot_arch and
propagate -Wl,--wrap=Dmod_Mutex_New to the firmware link via INTERFACE.

Co-authored-by: JohnAmadis <17320783+JohnAmadis@users.noreply.github.com>

Author: Copilot

src/arch/armv7/CMakeLists.txt

@@ -3,11 +3,16 @@
 # ======================================================================
 add_library(dmboot_arch STATIC
     dmod_critical.c
+    dmod_mutex.c
 )
 
 target_link_libraries(dmboot_arch
     PRIVATE 
         dmod
 )
 
+# Wrap Dmod_Mutex_New so the pre-RTOS guard is applied to all callers
+# (e.g. dmvfs) that are linked into the final firmware image.
+target_link_options(dmboot_arch INTERFACE -Wl,--wrap=Dmod_Mutex_New)
+
 add_subdirectory(${DMBOOT_ARCH_FAMILY})

src/arch/armv7/dmod_mutex.c

@@ -0,0 +1,36 @@
+/**
+ * @brief Pre-RTOS guard for Dmod_Mutex_New (ARMv7-M)
+ *
+ * The dmosi bridge library provides a strong Dmod_Mutex_New that calls
+ * dmosi_mutex_create(), which in turn calls pvPortMalloc() +
+ * xSemaphoreCreateRecursiveMutex().  Both succeed before vTaskStartScheduler()
+ * because FreeRTOS heap allocation does not require the scheduler.  However,
+ * dmosi_mutex_lock() returns -ENOTSUP when !dmosi_is_started(), so any caller
+ * that obtains a non-NULL mutex handle before the scheduler starts and then
+ * tries to lock it will fail.
+ *
+ * This wrapper (enabled via -Wl,--wrap=Dmod_Mutex_New) returns NULL when the
+ * scheduler has not yet been started.  NULL causes callers such as dmvfs to
+ * fall back to Dmod_EnterCritical / Dmod_ExitCritical (interrupt-disable
+ * critical sections), which work correctly both before and after RTOS start.
+ *
+ * After vTaskStartScheduler() the wrapper forwards to the real implementation
+ * so proper recursive RTOS mutexes are created as usual.
+ */
+
+#include <stdbool.h>
+
+/* Resolved at link time from dmosi_freertos */
+extern bool dmosi_is_started(void);
+
+/* The real (unwrapped) symbol comes from the dmosi bridge library */
+extern void* __real_Dmod_Mutex_New(bool Recursive);
+
+void* __wrap_Dmod_Mutex_New(bool Recursive)
+{
+    if (!dmosi_is_started())
+    {
+        return NULL;
+    }
+    return __real_Dmod_Mutex_New(Recursive);
+}