Support -Werror CLI argument to treat warnings as errors

The option is named "warningsAsErrors" in the Gradle plugin

 #KT-10563 Fixed

compiler/testData/cli/js-dce/dceHelp.out

@@ -8,4 +8,5 @@ where possible options include:
   -nowarn                    Generate no warnings
   -verbose                   Enable verbose logging output
   -version                   Display compiler version
+  -Werror                    Report an error if there are any warnings
 OK

compiler/testData/cli/js/jsHelp.out

@@ -25,4 +25,5 @@ where possible options include:
   -nowarn                    Generate no warnings
   -verbose                   Enable verbose logging output
   -version                   Display compiler version
+  -Werror                    Report an error if there are any warnings
 OK

compiler/testData/cli/jvm/help.out

@@ -23,4 +23,5 @@ where possible options include:
   -nowarn                    Generate no warnings
   -verbose                   Enable verbose logging output
   -version                   Display compiler version
+  -Werror                    Report an error if there are any warnings
 OK

compiler/testData/cli/jvm/werror.args

@@ -0,0 +1,4 @@
+$TESTDATA_DIR$/werror.kt
+-d
+$TEMP_DIR$
+-Werror

compiler/testData/cli/jvm/werror.kt

@@ -0,0 +1,4 @@
+fun foo(s: String, t: String?) {
+    s!!
+    t?.toString()
+}

compiler/testData/cli/jvm/werror.out

@@ -0,0 +1,5 @@
+error: warnings found and -Werror specified
+compiler/testData/cli/jvm/werror.kt:2:6: warning: unnecessary non-null assertion (!!) on a non-null receiver of type String
+    s!!
+     ^
+COMPILATION_ERROR

compiler/testData/cli/jvm/werrorWithExplicitError.args

@@ -0,0 +1,4 @@
+$TESTDATA_DIR$/werrorWithExplicitError.kt
+-d
+$TEMP_DIR$
+-Werror

compiler/testData/cli/jvm/werrorWithExplicitError.kt

@@ -0,0 +1,5 @@
+fun foo(s: String, t: String?) {
+    s!!
+    t?.toString()
+    t.length
+}

compiler/testData/cli/jvm/werrorWithExplicitError.out

@@ -0,0 +1,4 @@
+compiler/testData/cli/jvm/werrorWithExplicitError.kt:4:6: error: only safe (?.) or non-null asserted (!!.) calls are allowed on a nullable receiver of type String?
+    t.length
+     ^
+COMPILATION_ERROR

compiler/testData/cli/jvm/werrorWithNoWarn.args

@@ -0,0 +1,5 @@
+$TESTDATA_DIR$/werrorWithNoWarn.kt
+-d
+$TEMP_DIR$
+-Werror
+-nowarn

compiler/testData/cli/jvm/werrorWithNoWarn.kt

@@ -0,0 +1,4 @@
+fun foo(s: String, t: String?) {
+    s!!
+    t?.toString()
+}

compiler/testData/cli/jvm/werrorWithNoWarn.out

@@ -0,0 +1,5 @@
+error: warnings found and -Werror specified
+compiler/testData/cli/jvm/werrorWithNoWarn.kt:2:6: warning: unnecessary non-null assertion (!!) on a non-null receiver of type String
+    s!!
+     ^
+COMPILATION_ERROR

compiler/testData/cli/jvm/werrorWithStrongWarning.args

@@ -0,0 +1,6 @@
+$TESTDATA_DIR$/werrorWithStrongWarning.kt
+-d
+$TEMP_DIR$
+-Werror
+-cp
+non-existing-path.jar

compiler/testData/cli/jvm/werrorWithStrongWarning.kt

@@ -0,0 +1,4 @@
+fun foo(s: String, t: String?) {
+    s!!
+    t?.toString()
+}

compiler/testData/cli/jvm/werrorWithStrongWarning.out

@@ -0,0 +1,3 @@
+warning: classpath entry points to a non-existent location: non-existing-path.jar
+error: warnings found and -Werror specified
+COMPILATION_ERROR