[MNG-7340] Option fail-on-severity takes one argument

Closes #620
diff --git a/maven-embedder/src/main/java/org/apache/maven/cli/CLIManager.java b/maven-embedder/src/main/java/org/apache/maven/cli/CLIManager.java
index fc9c1bf..8708b5e 100644
--- a/maven-embedder/src/main/java/org/apache/maven/cli/CLIManager.java
+++ b/maven-embedder/src/main/java/org/apache/maven/cli/CLIManager.java
@@ -140,7 +140,7 @@
         options.addOption( Option.builder( ALTERNATE_GLOBAL_SETTINGS ).longOpt( "global-settings" ).desc( "Alternate path for the global settings file" ).hasArg().build() );
         options.addOption( Option.builder( Character.toString( ALTERNATE_USER_TOOLCHAINS ) ).longOpt( "toolchains" ).desc( "Alternate path for the user toolchains file" ).hasArg().build() );
         options.addOption( Option.builder( ALTERNATE_GLOBAL_TOOLCHAINS ).longOpt( "global-toolchains" ).desc( "Alternate path for the global toolchains file" ).hasArg().build() );
-        options.addOption( Option.builder( FAIL_ON_SEVERITY ).longOpt( "fail-on-severity" ).desc( "Configure which severity of logging should cause the build to fail" ).hasArgs().build() );
+        options.addOption( Option.builder( FAIL_ON_SEVERITY ).longOpt( "fail-on-severity" ).desc( "Configure which severity of logging should cause the build to fail" ).hasArg().build() );
         options.addOption( Option.builder( FAIL_FAST ).longOpt( "fail-fast" ).desc( "Stop at first failure in reactorized builds" ).build() );
         options.addOption( Option.builder( FAIL_AT_END ).longOpt( "fail-at-end" ).desc( "Only fail the build afterwards; allow all non-impacted builds to continue" ).build() );
         options.addOption( Option.builder( FAIL_NEVER ).longOpt( "fail-never" ).desc( "NEVER fail the build, regardless of project result" ).build() );