diff --git a/share/goa/lib/build/qmake.tcl b/share/goa/lib/build/qmake.tcl
index 73802cd..aded68d 100644
--- a/share/goa/lib/build/qmake.tcl
+++ b/share/goa/lib/build/qmake.tcl
@@ -1,12 +1,5 @@
-
-proc create_or_update_build_dir { } {
-
-	global cppflags cxxflags ldflags ldflags_so ldlibs_common
-	global ldlibs_exe ldlibs_so env
-	global config::build_dir config::project_dir config::abi_dir
-	global config::cross_dev_prefix config::arch config::project_name
-
-	set qt5_tool_dir "/usr/local/genode/tool/23.05/bin"
+proc _qmake_platform { } {
+	global config::arch
 
 	if {$arch == "x86_64"} {
 		set qmake_platform "genode-x86_64-g++"
@@ -16,6 +9,59 @@ proc create_or_update_build_dir { } {
 		exit_with_error "build via qmake failed: unsupported architecture: $arch\n"
 	}
 
+	return $qmake_platform
+}
+
+
+proc _qmake_build_cmd { qmake_platform } {
+	global cppflags cxxflags ldflags ldflags_so ldlibs_common
+	global ldlibs_exe ldlibs_so
+	global config::build_dir
+	global config::cross_dev_prefix
+
+	set qmake_cflags     "$cppflags $cxxflags "
+	append qmake_cflags "-D__GENODE__ -D__FreeBSD__=12 "
+	append qmake_cflags "-I$build_dir/qmake_root/include/QtCore/spec/$qmake_platform"
+
+	set qmake_ldlibs { }
+	lappend qmake_ldlibs -l:libc.lib.so
+	lappend qmake_ldlibs -l:libm.lib.so
+	lappend qmake_ldlibs -l:stdcxx.lib.so
+	lappend qmake_ldlibs -l:qt5_component.lib.so
+
+	set     cmd [sandboxed_build_command]
+	lappend cmd --setenv GENODE_QMAKE_CC           "${cross_dev_prefix}gcc"
+	lappend cmd --setenv GENODE_QMAKE_CXX          "${cross_dev_prefix}g++"
+	lappend cmd --setenv GENODE_QMAKE_LINK         "${cross_dev_prefix}g++"
+	lappend cmd --setenv GENODE_QMAKE_AR           "${cross_dev_prefix}ar"
+	lappend cmd --setenv GENODE_QMAKE_OBJCOPY      "${cross_dev_prefix}objcopy"
+	lappend cmd --setenv GENODE_QMAKE_NM           "${cross_dev_prefix}nm"
+	lappend cmd --setenv GENODE_QMAKE_STRIP        "${cross_dev_prefix}strip"
+	lappend cmd --setenv GENODE_QMAKE_CFLAGS       "$qmake_cflags"
+	lappend cmd --setenv GENODE_QMAKE_LFLAGS_APP   "$ldflags $ldlibs_common $ldlibs_exe $qmake_ldlibs"
+	lappend cmd --setenv GENODE_QMAKE_LFLAGS_SHLIB "$ldflags_so $ldlibs_common $ldlibs_so $qmake_ldlibs"
+
+	#
+	# libgcc must appear on the command line after all other libs
+	# (including those added by qmake) and using the QMAKE_LIBS
+	# variable achieves this, fortunately
+	#
+	lappend cmd --setenv GENODE_QMAKE_LIBS "-lgcc"
+
+	return $cmd
+}
+
+
+proc create_or_update_build_dir { } {
+
+	global cppflags cxxflags ldflags ldflags_so ldlibs_common
+	global ldlibs_exe ldlibs_so
+	global config::build_dir config::project_dir config::abi_dir
+	global config::cross_dev_prefix config::project_name
+
+	set qt5_tool_dir "/usr/local/genode/tool/23.05/bin"
+	set qmake_platform [_qmake_platform]
+
 	if {![file exists $build_dir]} {
 		file mkdir $build_dir }
 
@@ -31,7 +77,6 @@ proc create_or_update_build_dir { } {
 	file link -symbolic qmake_root/include [file join [api_archive_dir $qt5_api] include]
 	file link -symbolic qmake_root/lib $abi_dir
 
-
 	file mkdir qmake_root/mkspecs
 	file link -symbolic qmake_root/mkspecs/common            [file join [api_archive_dir $qt5_api] mkspecs common]
 	file link -symbolic qmake_root/mkspecs/features          [file join [api_archive_dir $qt5_api] mkspecs features]
@@ -41,43 +86,16 @@ proc create_or_update_build_dir { } {
 	file link -symbolic qmake_root/mkspecs/qconfig.pri       $qmake_platform/qconfig.pri
 	file link -symbolic qmake_root/mkspecs/qmodule.pri       $qmake_platform/qmodule.pri
 
-	set qmake_cflags     "$cppflags $cxxflags "
-	append qmake_cflags "-D__GENODE__ -D__FreeBSD__=12 "
-	append qmake_cflags "-I$build_dir/qmake_root/include/QtCore/spec/$qmake_platform"
-
-	set qmake_ldlibs { }
-	lappend qmake_ldlibs -l:libc.lib.so
-	lappend qmake_ldlibs -l:libm.lib.so
-	lappend qmake_ldlibs -l:stdcxx.lib.so
-	lappend qmake_ldlibs -l:qt5_component.lib.so
-
-	set ::env(GENODE_QMAKE_CC)           "${cross_dev_prefix}gcc"
-	set ::env(GENODE_QMAKE_CXX)          "${cross_dev_prefix}g++"
-	set ::env(GENODE_QMAKE_LINK)         "${cross_dev_prefix}g++"
-	set ::env(GENODE_QMAKE_AR)           "${cross_dev_prefix}ar"
-	set ::env(GENODE_QMAKE_OBJCOPY)      "${cross_dev_prefix}objcopy"
-	set ::env(GENODE_QMAKE_NM)           "${cross_dev_prefix}nm"
-	set ::env(GENODE_QMAKE_STRIP)        "${cross_dev_prefix}strip"
-	set ::env(GENODE_QMAKE_CFLAGS)       "$qmake_cflags"
-	set ::env(GENODE_QMAKE_LFLAGS_APP)   "$ldflags $ldlibs_common $ldlibs_exe $qmake_ldlibs"
-	set ::env(GENODE_QMAKE_LFLAGS_SHLIB) "$ldflags_so $ldlibs_common $ldlibs_so $qmake_ldlibs"
-
-	#
-	# libgcc must appear on the command line after all other libs
-	# (including those added by qmake) and using the QMAKE_LIBS
-	# variable achieves this, fortunately
-	#
-	set ::env(GENODE_QMAKE_LIBS) "-lgcc"
+	cd $orig_pwd
 
 	set qt_conf "qmake_root/mkspecs/$qmake_platform/qt.conf"
-	set cmd [list [file join $qt5_tool_dir qmake] -qtconf $qt_conf [file join $project_dir src]]
+	set     cmd [_qmake_build_cmd $qmake_platform]
+	lappend cmd [file join $qt5_tool_dir qmake] -qtconf $qt_conf [file join $project_dir src]
 
-	diag "create build directory via command:" {*}$cmd
+	diag "create build directory via qmake"
 
 	if {[catch {exec -ignorestderr {*}$cmd | sed "s/^/\[$project_name:qmake\] /" >@ stdout} msg]} {
 		exit_with_error "build-directory creation via qmake failed:\n" $msg }
-
-	cd $orig_pwd
 }
 
 
@@ -85,7 +103,8 @@ proc build { } {
 	global verbose
 	global config::build_dir config::jobs config::project_name
 
-	set cmd [list make -C $build_dir "-j$jobs"]
+	set     cmd [_qmake_build_cmd [_qmake_platform]]
+	lappend cmd make -C $build_dir "-j$jobs"
 
 	if {$verbose == 0} {
 		lappend cmd "-s"