py-petsc4py: patch again for wrong assumption on LDSHARED

var/spack/repos/builtin/packages/py-petsc4py/ldshared.patch

@@ -7,7 +7,7 @@ index 8a2466a5bd..73c08b923a 100644
          ldflags = getenv('LDFLAGS', cflags + ' ' + (ldflags or ''))
          ldcmd = split_quoted(ld) + split_quoted(ldflags)
 -        ldshared = [flg for flg in split_quoted(ldshared) if flg not in ldcmd]
-+        ldshared = [flg for flg in split_quoted(ldshared) if flg not in ldcmd and (flg.find('/lib/spack/env')<0)]
++        ldshared = [flg for flg in split_quoted(ldshared) if flg not in ldcmd and (flg.find('/libexec/spack')<0)]
          ldshared = str.join(' ', ldshared)
          #
          def get_flags(cmd):

var/spack/repos/builtin/packages/py-petsc4py/ldshared_319.patch

@@ -0,0 +1,12 @@
+diff --unified --recursive --no-dereference spack-src1/conf/confpetsc.py spack-src2/conf/confpetsc.py
+--- spack-src1/conf/confpetsc.py	2025-02-17 13:02:08.781676798 +0100
++++ spack-src2/conf/confpetsc.py	2025-02-17 13:03:13.024625112 +0100
+@@ -350,7 +350,7 @@
+         ldshared = [
+             flg
+             for flg in split_quoted(ldshared)
+-            if flg not in ldcmd and (flg.find('/lib/spack/env') < 0)
++            if flg not in ldcmd and (flg.find('/libexec/spack/') < 0)
+         ]
+         ldshared = str.join(' ', ldshared)
+ 

var/spack/repos/builtin/packages/py-petsc4py/package.py

@@ -93,6 +93,9 @@ class PyPetsc4py(PythonPackage):
 
     variant("mpi", default=True, description="Activates MPI support")
 
+    # Hack to fix https://github.com/spack/spack/issues/21451, where Petsc4Py expects LDSHARED
+    # to start with the same executable as get_config_var("CC")
+    patch("ldshared_319.patch", when="@3.19:")
     patch("ldshared.patch", when="@:3.18")
 
     depends_on("py-cython@3:", when="@3.20:", type="build")