linux-user: Create target/elfload.c files

Prepare to split the main linux-user/elfload.c.
Create empty files for each target, and add the common build rule.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

meson.build

@@ -4327,7 +4327,11 @@ foreach target : target_dirs
     )
     if 'CONFIG_LINUX_USER' in config_target
       dir = base_dir / abi
-      arch_srcs += files(dir / 'signal.c', dir / 'cpu_loop.c')
+      arch_srcs += files(
+        dir / 'cpu_loop.c',
+        dir / 'elfload.c',
+        dir / 'signal.c',
+      )
       if config_target.has_key('TARGET_SYSTBL_ABI')
         arch_srcs += \
           syscall_nr_generators[abi].process(base_dir / abi / config_target['TARGET_SYSTBL'],