octave: use pcre2 for @8: (#42636)

* octave: use pcre2 for @8:

* Add 'pcre2' variant to octave to control pcre vs. pcre2

* Update var/spack/repos/builtin/packages/octave/package.py

Co-authored-by: Alec Scott <hi@alecbcs.com>

---------

Co-authored-by: Alex Richert <alexander.richert@noaa.gov>
Co-authored-by: Alec Scott <hi@alecbcs.com>

var/spack/repos/builtin/packages/octave/package.py

@@ -72,6 +72,7 @@ class Octave(AutotoolsPackage, GNUMirrorPackage):
     variant("jdk", default=False, description="Use Java")
     variant("llvm", default=False, description="Use LLVM")
     variant("opengl", default=False, description="Use OpenGL")
+    variant("pcre2", default=True, when="@8:", description="Use PCRE2 instead of PCRE")
     variant("qhull", default=False, description="Use qhull")
     variant("qrupdate", default=False, description="Use qrupdate")
     variant("qscintilla", default=False, description="Use QScintill")
@@ -84,7 +85,9 @@ class Octave(AutotoolsPackage, GNUMirrorPackage):
     depends_on("lapack")
     # Octave does not configure with sed from darwin:
     depends_on("sed", when=sys.platform == "darwin", type="build")
-    depends_on("pcre")
+    depends_on("pcre", when="@:7")
+    depends_on("pcre", when="~pcre2")
+    depends_on("pcre2", when="+pcre2")
     depends_on("pkgconfig", type="build")
     depends_on("texinfo", type="build")
 
@@ -350,6 +353,8 @@ def configure_args(self):
         else:
             config_args.append("--without-z")
 
+        if spec.satisfies("~pcre2"):
+            config_args.append("--without-pcre2")
         # If 64-bit BLAS is used:
         if (
             spec.satisfies("^openblas+ilp64")