Ignore failing incremental tests for GCC backend

tests/incremental/thinlto/cgu_invalidated_via_import.rs

@@ -5,6 +5,7 @@
 //@ revisions: cfail1 cfail2 cfail3
 //@ compile-flags: -Z query-dep-graph -O
 //@ build-pass
+//@ ignore-backends: gcc
 
 #![feature(rustc_attrs)]
 #![crate_type="rlib"]

tests/incremental/thinlto/cgu_invalidated_when_export_added.rs

@@ -1,5 +1,6 @@
 //@ revisions: cfail1 cfail2
 //@ build-pass
+//@ ignore-backends: gcc
 
 // rust-lang/rust#69798:
 //

tests/incremental/thinlto/cgu_invalidated_when_export_removed.rs

@@ -1,5 +1,6 @@
 //@ revisions: cfail1 cfail2
 //@ build-pass
+//@ ignore-backends: gcc
 
 // rust-lang/rust#69798:
 //

tests/incremental/thinlto/cgu_invalidated_when_import_added.rs

@@ -1,6 +1,7 @@
 //@ revisions: cfail1 cfail2
 //@ compile-flags: -O -Zhuman-readable-cgu-names -Cllvm-args=-import-instr-limit=10
 //@ build-pass
+//@ ignore-backends: gcc
 
 // rust-lang/rust#59535:
 //

tests/incremental/thinlto/cgu_invalidated_when_import_removed.rs

@@ -1,6 +1,7 @@
 //@ revisions: cfail1 cfail2
 //@ compile-flags: -O -Zhuman-readable-cgu-names -Cllvm-args=-import-instr-limit=10
 //@ build-pass
+//@ ignore-backends: gcc
 
 // rust-lang/rust#59535:
 //

tests/incremental/thinlto/cgu_keeps_identical_fn.rs

@@ -6,6 +6,7 @@
 //@ revisions: cfail1 cfail2 cfail3
 //@ compile-flags: -Z query-dep-graph -O
 //@ build-pass
+//@ ignore-backends: gcc
 
 #![feature(rustc_attrs)]
 #![crate_type = "rlib"]

tests/incremental/thinlto/independent_cgus_dont_affect_each_other.rs

@@ -4,6 +4,7 @@
 //@ revisions: cfail1 cfail2 cfail3
 //@ compile-flags: -Z query-dep-graph -O
 //@ build-pass
+//@ ignore-backends: gcc
 
 #![feature(rustc_attrs)]
 #![crate_type="rlib"]