BUG: Allow '.' and '+' in -march/-mtune strip regex (issue #6133)

Backport of the main-branch fix to release-5.4 for inclusion in 5.4.7.

The aggressive optimization flag stripping in
generate_castxml_commandline_flags() must remove -march=/-mtune=
arguments before feeding the compiler line to castxml, because
castxml's bundled clang preprocessor does not accept all backend
target features. The previous regex character class
[a-zA-Z0-9\-]* stopped at the first non-alphanumeric, non-hyphen
character, so extended target descriptors silently lost their tail:

  -march=armv8.2-a+fp16+rcpc+dotprod+crypto
       ^^^^^^^^^                              <-- only this much matched
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ <-- this remained verbatim

The leftover fragment ".2-a+fp16+rcpc+dotprod+crypto" was then
passed to clang as a positional argument, producing:

  clang++: error: no such file or directory: '.2-a+fp16+rcpc+dotprod+crypto'

Reported on Arch Linux aarch64 against ITK 5.4.6. The same class
of breakage applies to extended x86 names like -march=znver3 or
-march=skylake-avx512.

Extend the character class to [A-Za-z0-9._+\-]* so the entire token
is matched and stripped.

Author: hjmjohnson

Wrapping/macro_files/itk_auto_load_submodules.cmake

@@ -25,8 +25,14 @@ function(generate_castxml_commandline_flags)
     set(_castxml_cc_flags "${_castxml_cc_flags} ${CMAKE_CXX${CMAKE_CXX_STANDARD}_STANDARD_COMPILE_OPTION}")
   endif()
 
-  # Aggressive optimization flags cause cast_xml to give invalid error conditions
-  set(INVALID_OPTIMIZATION_FLAGS "-fopenmp;-march=[a-zA-Z0-9\-]*;-mtune=[a-zA-Z0-9\-]*;-mfma")
+  # Aggressive optimization flags cause cast_xml to give invalid error conditions.
+  # The -march=/-mtune= character class must accept '.', '+', and '_' so that
+  # extended ARM/x86 targets such as -march=armv8.2-a+fp16+rcpc+dotprod+crypto
+  # or -march=znver3 are stripped as a single token. The previous class
+  # [a-zA-Z0-9\-]* stopped at the first '.' or '+', leaving a dangling tail
+  # (e.g. ".2-a+fp16+rcpc+dotprod+crypto") that clang then misinterpreted as
+  # a positional file argument. See InsightSoftwareConsortium/ITK#6133.
+  set(INVALID_OPTIMIZATION_FLAGS "-fopenmp;-march=[A-Za-z0-9._+\-]*;-mtune=[A-Za-z0-9._+\-]*;-mfma")
   foreach(rmmatch ${INVALID_OPTIMIZATION_FLAGS})
     string(
       REGEX