semihosting: Build stubs once

Move stubs to the global stub_ss[] source set. These files
are now built once for all binaries, instead of one time
per system binary.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20260225035739.42848-12-philmd@linaro.org>

semihosting/meson.build

@@ -1,4 +1,4 @@
-common_ss.add(when: 'CONFIG_SEMIHOSTING', if_false: files('stubs-all.c'))
+stub_ss.add(files('stubs-all.c'))
 user_ss.add(when: 'CONFIG_SEMIHOSTING', if_true: files(
   'user.c',
   'guestfd.c'))
@@ -8,12 +8,13 @@ system_ss.add(when: 'CONFIG_SEMIHOSTING', if_true: files(
   'guestfd.c',
   'uaccess.c',
   'syscalls.c',
-), if_false: files(
+))
+stub_ss.add(files(
   'stubs-system.c',
 ))
 system_ss.add(when: 'CONFIG_ARM_COMPATIBLE_SEMIHOSTING',
-  if_true: files('arm-compat-semi.c'),
-  if_false: files('arm-compat-semi-stub.c'))
+  if_true: files('arm-compat-semi.c'))
+stub_ss.add(files('arm-compat-semi-stub.c'))
 
 specific_ss.add(when: ['CONFIG_SEMIHOSTING', 'CONFIG_USER_ONLY'],
                 if_true: files('syscalls.c'))