internal/rosa: replace busybox dash with mksh

Toybox does not provide a shell, mksh fills that gap.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/rosa/gnu.go

@@ -59,6 +59,7 @@ func (t Toolchain) newAutoconf() pkg.Artifact {
 		t.Load(Make),
 		t.Load(M4),
 		t.Load(Perl),
+		t.Load(Bash),
 	}, nil, nil, `
 cd "$(mktemp -d)"
 /usr/src/autoconf/configure \
@@ -205,6 +206,7 @@ func (t Toolchain) newCoreutils() pkg.Artifact {
 	return t.New("coreutils-"+version, false, []pkg.Artifact{
 		t.Load(Make),
 		t.Load(Perl),
+		t.Load(Bash),
 
 		t.Load(KernelHeaders),
 	}, nil, nil, `
@@ -212,6 +214,8 @@ cd /usr/src/coreutils
 test_disable() { chmod +w "$2" && echo "$1" > "$2"; }
 
 test_disable '#!/bin/sh' gnulib-tests/test-c32ispunct.sh
+test_disable '#!/bin/sh' tests/split/line-bytes.sh
+test_disable '#!/bin/sh' tests/dd/no-allocate.sh
 
 cd "$(mktemp -d)"
 /usr/src/coreutils/configure \