[lld] [LLD] Add CLASS syntax to SECTIONS (PR #95323)

[Fangrui Song via llvm-commits]

================
@@ -198,13 +198,52 @@ the current location to a max-page-size boundary, ensuring that the next
 LLD will insert ``.relro_padding`` immediately before the symbol assignment
 using ``DATA_SEGMENT_RELRO_END``.
 
+Section Classes
+~~~~~~~~~~~~~~~
+
+``SECTIONS`` commands can define classes of input sections:
+
+::
+
+  SECTIONS {
+    CLASS(class_name) {
+      input-section-description
+      input-section-description
+      ...
+    }
+  }
+
+Input section descriptions can refer to a class using ``CLASS(class_name)``
+instead of the usual filename and section name patterns. For example:
+
+::
+
+  SECTIONS {
+    CLASS(c) { *(.rodata.earlier) }
+    .rodata { *(.rodata) CLASS(c) (*.rodata.later) }
----------------
MaskRay wrote:

`CLASS` could be a file name, conflicting with existing script. But we can accept the risk, and users could use `"CLASS"(.text)` if they want to use `CLASS` as the file name...

https://github.com/llvm/llvm-project/pull/95323