common: make multi arch actually work for builds

userland: create --static to make build a bit easier

Manually forward --dry-run to test-userland.

README.adoc

@@ -2944,7 +2944,7 @@ You can also try statically linked executables with:
 ....
 ./build-userland \
   --arch aarch64 \
-  --make-args='CCFLAGS_EXTRA=-static' \
+  --static \
   --userland-build-id static \
 ;
 ./run \
@@ -2961,7 +2961,7 @@ Or you can run statically linked built by the host packaged toolchain with:
 ./build-userland \
   --arch aarch64 \
   --host \
-  --make-args='-B CFLAGS_EXTRA=-static' \
+  --static \
   --userland-build-id host-static \
 ;
 ./run \
@@ -3036,8 +3036,8 @@ So let's just play with some static ones:
 ....
 ./build-userland \
   --arch aarch64 \
+  --static \
   --userland-build-id static \
-  --make-args='CCFLAGS_EXTRA=-static' \
 ;
 ./run \
   --arch aarch64 \
@@ -3158,7 +3158,9 @@ Result on <<p51>> at bad30f513c46c1b0995d3a10c0d9bc2a33dc4fa0:
 Automatically run non-interactive userland tests that don't depend on nay kernel modules:
 
 ....
-./test-userland
+./build-userland --all-archs
+./build-userland --all-archs --static --userland-build-id static
+./test-userland --all-archs
 ....
 
 Source: link:test-userland[]