Add the ability to generate JUnit XML reports with a -J flag

If the -J flag is passed, generate JUnit XML reports for each check, in-line with how Java tools generate JUnit reports.
Check section numbers equate to 'root packages', checks are second-level packages, each check equates to a testsuite (mirroring Java where each test class is a testsuite) and each pass/fail of a check equates to a testcase
Time the execution of each check and include this in the report
Include properties (Prowler version, check level etc.) in-line with standard JUnit files
XML escape all strings for safety

Detect if a user has GNU coreutils installed on Mac OS X, but not as their default, switching to using gdate for date commands if so, as it has more features, including getting dates in milliseconds
Add prowler-output, junit-reports and VSCode files to .gitignore
Update README to include JUnit info, address markdownlint warnings
Remove unused arguments to jq in generateJsonAsffOutput

Fixes #537

include/junit_integration

@@ -0,0 +1,89 @@
+#!/usr/bin/env bash
+
+# Prowler - the handy cloud security tool (copyright 2018) by Toni de la Fuente
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may not
+# use this file except in compliance with the License. You may obtain a copy
+# of the License at http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software distributed
+# under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
+# CONDITIONS OF ANY KIND, either express or implied. See the License for the
+# specific language governing permissions and limitations under the License.
+
+# Generates JUnit XML reports which can be read by Jenkins or other CI tools
+
+JUNIT_OUTPUT_DIRECTORY="junit-reports"
+
+xml_escape() {
+  sed 's/&/\&amp;/g; s/</\&lt;/g; s/>/\&gt;/g; s/\"/\&quot;/g; s/'"'"'/\&#39;/g' <<< "$1"
+}
+
+prepare_junit_output() {
+  # Remove any JUnit output from previous runs
+  rm -rf "$JUNIT_OUTPUT_DIRECTORY"
+  mkdir "$JUNIT_OUTPUT_DIRECTORY"
+  echo ""
+  echo "$NOTICE Writing JUnit XML reports to $PROWLER_DIR/$JUNIT_OUTPUT_DIRECTORY $NORMAL"
+}
+
+prepare_junit_check_output() {
+  # JUnit test cases must be named uniquely, but each Prowler check can output many times due to multiple resources,
+  # therefore append an index value to the test case name to provide uniqueness, reset it to 1 before starting this check
+  JUNIT_CHECK_INDEX=1
+  # To match JUnit behaviour in Java, and ensure that an aborted execution does not leave a partially written and therefore invalid XML file,
+  # output a JUnit XML file per check
+  JUNIT_OUTPUT_FILE="$JUNIT_OUTPUT_DIRECTORY/$1.xml"
+  printf '%s\n' \
+    "<?xml version=\"1.0\" encoding=\"UTF-8\"?>" \
+    "<testsuite name=\"$(xml_escape "$(get_junit_classname)")\" timestamp=\"$(get_iso8601_timestamp)\">" \
+    "  <properties>" \
+    "    <property name=\"prowler.version\" value=\"$(xml_escape "$PROWLER_VERSION")\"/>" \
+    "    <property name=\"aws.profile\" value=\"$(xml_escape "$PROFILE")\"/>" \
+    "    <property name=\"aws.accountNumber\" value=\"$(xml_escape "$ACCOUNT_NUM")\"/>" \
+    "    <property name=\"check.id\" value=\"$(xml_escape "$TITLE_ID")\"/>" \
+    "    <property name=\"check.scored\" value=\"$(xml_escape "$ITEM_SCORED")\"/>" \
+    "    <property name=\"check.level\" value=\"$(xml_escape "$ITEM_LEVEL")\"/>" \
+    "    <property name=\"check.asff.type\" value=\"$(xml_escape "$ASFF_TYPE")\"/>" \
+    "    <property name=\"check.asff.resourceType\" value=\"$(xml_escape "$ASFF_RESOURCE_TYPE")\"/>" \
+    "  </properties>" \
+    > "$JUNIT_OUTPUT_FILE"
+  JUNIT_CHECK_START_TIME=$(get_time_in_milliseconds)
+}
+
+finalise_junit_check_output() {
+  echo '</testsuite>' >> "$JUNIT_OUTPUT_FILE"
+}
+
+output_junit_success() {
+  output_junit_test_case "$1" "<system-out>$(xml_escape "$1")</system-out>"
+}
+
+output_junit_info() {
+  # Nothing to output for JUnit for this level of message, but reset the check timer for timing the next check
+  JUNIT_CHECK_START_TIME=$(get_time_in_milliseconds)
+}
+
+output_junit_failure() {
+  output_junit_test_case "$1" "<failure message=\"$(xml_escape "$1")\"/>"
+}
+
+get_junit_classname() {
+  # <section>.<check_id> naturally follows a Java package structure, so it is suitable as a package name
+  echo "$TITLE_ID"
+}
+
+output_junit_test_case() {
+  local time_now
+  local test_case_duration
+  time_now=$(get_time_in_milliseconds)
+  # JUnit test case time values are in seconds, so divide by 1000 using e-3 to convert from milliseconds without losing accuracy due to non-floating point arithmetic
+  test_case_duration=$(printf "%.3f" "$(("$time_now" - "$JUNIT_CHECK_START_TIME"))e-3")
+  printf '%s\n' \
+    "  <testcase name=\"$(xml_escape "$TITLE_TEXT") ($JUNIT_CHECK_INDEX)\" classname=\"$(xml_escape "$(get_junit_classname)")\" time=\"$test_case_duration\">" \
+    "    $2" \
+    "  </testcase>" >> "$JUNIT_OUTPUT_FILE"
+  # Reset the check timer for timing the next check
+  JUNIT_CHECK_START_TIME=$(get_time_in_milliseconds)
+  ((JUNIT_CHECK_INDEX+=1))
+}