asm,cortex-m: Add warning at configure time if soc bus definition is …

…missing.

This may help while porting to new SoC.

kernel/include/sentry/arch/asm-cortex-m/meson.build

@@ -45,6 +45,12 @@ core_h = custom_target('gen_core',
     command: [ jinja_cli, '-d', svd_json, '-o', '@OUTPUT@', '@INPUT@' ],
 )
 
+arch_header_set.add(
+    irq_def_h.to_list(),
+    layout_h.to_list(),
+    core_h.to_list(),
+)
+
 # the way we generate the buses list depend on the SoC family. To do
 # that, the input jinja template is selected depending on the configured SOC
 # family or subfamily
@@ -58,16 +64,15 @@ buses_h_in_set.add(when: 'CONFIG_SOC_SUBFAMILY_STM32U5', if_true: files('stm32l4
 # here, we can add other templates for other ARM SoC famillies if needed
 buses_h_in_set_config = buses_h_in_set.apply(kconfig_data, strict: false)
 
-buses_h = custom_target('gen_buses',
-    input: buses_h_in_set_config.sources(),
-    output: 'buses.h',
-    depends: [ svd_json ],
-    command: [ jinja_cli, '-d', svd_json, '-o', '@OUTPUT@', '--define', 'NAME', 'RCC', '@INPUT@' ],
-)
+if buses_h_in_set_config.sources().length() != 0
+    buses_h = custom_target('gen_buses',
+        input: buses_h_in_set_config.sources(),
+        output: 'buses.h',
+        depends: [ svd_json ],
+        command: [ jinja_cli, '-d', svd_json, '-o', '@OUTPUT@', '--define', 'NAME', 'RCC', '@INPUT@' ],
+    )
 
-arch_header_set.add(
-    irq_def_h.to_list(),
-    layout_h.to_list(),
-    core_h.to_list(),
-    buses_h.to_list(),
-)
+    arch_header_set.add(buses_h.to_list())
+else
+    warning('Missing bus definition for SoC @0@'.format(kconfig_data.get('CONFIG_ARCH_SOCNAME')))
+endif