PellesC: Document support for this compiler

This was left out of commit b7a5f2732d (PellesC: Add minimal support for
this C compiler, 2026-04-03) because the implementation was not usable
in general.  It is now.

Closes: #21536
Co-authored-by: Serguei E. Leontiev <leo@sai.msu.ru>

Help/command/include/SUPPORTED_LANGUAGES.rst

@@ -51,7 +51,7 @@ The supported languages are:
 ``ASM_MASM``
   Microsoft Assembler (x86, x64)
 
-.. FIXME(#21536): ``ASM_POASM``
+``ASM_POASM``
   .. versionadded:: 4.4
 
   Pelles C toolchain assembler.

Help/envvar/ASM_DIALECT.rst

@@ -14,7 +14,7 @@ files. ``ASM<DIALECT>`` can be one of:
 
 * ``ASM_MARMASM`` (Microsoft ARM Assembler)
 
-.. FIXME(#21536): * ``ASM_POASM`` (Pelles Macro Assembler)
+* ``ASM_POASM`` (Pelles Macro Assembler)
 
 * ``ASM-ATT`` (Assembler AT&T)
 

Help/envvar/ASM_DIALECTFLAGS.rst

@@ -14,7 +14,7 @@ of an assembly language.  ``ASM<DIALECT>FLAGS`` can be one of:
 
 * ``ASM_MARMASMFLAGS``
 
-.. FIXME(#21536): * ``ASM_POASMFLAGS``
+* ``ASM_POASMFLAGS``
 
 * ``ASM-ATTFLAGS``
 

Help/release/dev/pellesc-compiler.rst

@@ -0,0 +1,9 @@
+pellesc-compiler
+----------------
+
+* The `Pelles C`_ toolchain is now supported with compiler id ``PellesC``.
+
+* The ``ASM_POASM`` language was added to support the `Pelles C`_
+  toolchain's Macro Assembler.
+
+.. _`Pelles C`: https://pellesc.se

Help/variable/CMAKE_LANG_COMPILER_ID.rst

@@ -39,6 +39,7 @@ Value                           Name
 ``NVIDIA``                      `NVIDIA CUDA Compiler`_
 ``OrangeC``                     `OrangeC Compiler`_
 ``OpenWatcom``                  `Open Watcom`_
+``PellesC``                     `Pelles C`_
 ``PGI``                         The Portland Group
 ``PathScale``                   PathScale
 ``QCC``                         QNX C/C++ compiler
@@ -71,6 +72,7 @@ languages.
 .. _NVIDIA CUDA Compiler: https://developer.nvidia.com/cuda-llvm-compiler
 .. _Open Watcom: https://open-watcom.github.io
 .. _OrangeC Compiler: https://github.com/LADSoft/OrangeC
+.. _Pelles C: https://pellesc.se
 .. _Renesas Compiler: https://www.renesas.com
 .. _Small Device C Compiler: https://sdcc.sourceforge.net
 .. _Tiny C Compiler: https://bellard.org/tcc