test: Add loongarch64-linux-(none,musl,gnu) to the test matrix.

Currently skips std tests which have many issues.

Author: alexrp

test/tests.zig

@@ -497,6 +497,33 @@ const test_targets = blk: {
             .pic = false, // Long calls don't work with PIC.
         },
 
+        .{
+            .target = .{
+                .cpu_arch = .loongarch64,
+                .os_tag = .linux,
+                .abi = .none,
+            },
+            .skip_modules = &.{"std"},
+        },
+        .{
+            .target = .{
+                .cpu_arch = .loongarch64,
+                .os_tag = .linux,
+                .abi = .musl,
+            },
+            .link_libc = true,
+            .skip_modules = &.{"std"},
+        },
+        .{
+            .target = .{
+                .cpu_arch = .loongarch64,
+                .os_tag = .linux,
+                .abi = .gnu,
+            },
+            .link_libc = true,
+            .skip_modules = &.{"std"},
+        },
+
         .{
             .target = .{
                 .cpu_arch = .mips,