Use bash in prepare scripts (#339)

Prepare scripts that use `#!/bin/sh` and
`source "$HOME/.sdkman/bin/sdkman-init.sh"`
fail on systems where `sh` is not `bash`,
e.g. on Ubuntu it is `dash` which has not `source`.

prepare_hundredwatt.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 #
 #  Copyright 2023 The original authors
 #
@@ -15,6 +15,5 @@
 #  limitations under the License.
 #
 
-
 source "$HOME/.sdkman/bin/sdkman-init.sh"
 sdk use java 21.0.1-graal

prepare_kuduwa-keshavram.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 #
 #  Copyright 2023 The original authors
 #

prepare_mtopolnik.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 #
 #  Copyright 2023 The original authors
 #

prepare_ricardopieper.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 #
 #  Copyright 2023 The original authors
 #

prepare_roman-r-m.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 #
 #  Copyright 2023 The original authors
 #
@@ -16,4 +16,4 @@
 #
 
 source "$HOME/.sdkman/bin/sdkman-init.sh"
-sdk use java 21.0.1-graal 1>&2
+sdk use java 21.0.1-graal 1>&2