Add some negative test coverage for -Zlinker-features flag

Author: jieyouxu

tests/ui/linking/linker-features-malformed.invalid_modifier.stderr

@@ -0,0 +1,2 @@
+error: incorrect value `*lld` for unstable option `linker-features` - a list of enabled (`+` prefix) and disabled (`-` prefix) features: `lld` was expected
+

tests/ui/linking/linker-features-malformed.invalid_separator.stderr

@@ -0,0 +1,2 @@
+error: incorrect value `-lld@+lld` for unstable option `linker-features` - a list of enabled (`+` prefix) and disabled (`-` prefix) features: `lld` was expected
+

tests/ui/linking/linker-features-malformed.no_value.stderr

@@ -0,0 +1,2 @@
+error: incorrect value `` for unstable option `linker-features` - a list of enabled (`+` prefix) and disabled (`-` prefix) features: `lld` was expected
+

tests/ui/linking/linker-features-malformed.rs

@@ -0,0 +1,27 @@
+//! Check that malformed `-Zlinker-features` flags are properly rejected.
+
+//@ revisions: no_value
+//@[no_value] compile-flags: -Zlinker-features=
+//[no_value]~? ERROR incorrect value `` for unstable option `linker-features`
+
+//@ revisions: invalid_modifier
+//@[invalid_modifier] compile-flags: -Zlinker-features=*lld
+//[invalid_modifier]~? ERROR incorrect value `*lld` for unstable option `linker-features`
+
+//@ revisions: unknown_value
+//@[unknown_value] compile-flags: -Zlinker-features=unknown
+//[unknown_value]~? ERROR incorrect value `unknown` for unstable option `linker-features`
+
+//@ revisions: unknown_modifier_value
+//@[unknown_modifier_value] compile-flags: -Zlinker-features=-unknown
+//[unknown_modifier_value]~? ERROR incorrect value `-unknown` for unstable option `linker-features`
+
+//@ revisions: unknown_boolean
+//@[unknown_boolean] compile-flags: -Zlinker-features=maybe
+//[unknown_boolean]~? ERROR incorrect value `maybe` for unstable option `linker-features`
+
+//@ revisions: invalid_separator
+//@[invalid_separator] compile-flags: -Zlinker-features=-lld@+lld
+//[invalid_separator]~? ERROR incorrect value `-lld@+lld` for unstable option `linker-features`
+
+fn main() {}

tests/ui/linking/linker-features-malformed.unknown_boolean.stderr

@@ -0,0 +1,2 @@
+error: incorrect value `maybe` for unstable option `linker-features` - a list of enabled (`+` prefix) and disabled (`-` prefix) features: `lld` was expected
+

tests/ui/linking/linker-features-malformed.unknown_modifier_value.stderr

@@ -0,0 +1,2 @@
+error: incorrect value `-unknown` for unstable option `linker-features` - a list of enabled (`+` prefix) and disabled (`-` prefix) features: `lld` was expected
+

tests/ui/linking/linker-features-malformed.unknown_value.stderr

@@ -0,0 +1,2 @@
+error: incorrect value `unknown` for unstable option `linker-features` - a list of enabled (`+` prefix) and disabled (`-` prefix) features: `lld` was expected
+