IntelOneApiPackage: add envmods variant to toggle environment modifications by oneapi packages (#34253)

Co-authored-by: Sean Koyama <skoyama@anl.gov>
Co-authored-by: Robert Cohn <robert.s.cohn@intel.com>

2 files changed, 18 insertions, 7 deletions

diff --git a/lib/spack/spack/build_systems/oneapi.py b/lib/spack/spack/build_systems/oneapi.py
index 9f009918fd..b7456a5775 100644
--- a/lib/spack/spack/build_systems/oneapi.py
+++ b/lib/spack/spack/build_systems/oneapi.py
@@ -10,7 +10,7 @@ from os.path import basename, dirname, isdir
 
 from llnl.util.filesystem import find_headers, find_libraries, join_path
 
-from spack.directives import conflicts
+from spack.directives import conflicts, variant
 from spack.util.environment import EnvironmentModifications
 from spack.util.executable import Executable
 
@@ -36,6 +36,13 @@ class IntelOneApiPackage(Package):
     ]:
         conflicts(c, msg="This package in only available for x86_64 and Linux")
 
+    # Add variant to toggle environment modifications from vars.sh
+    variant(
+        "envmods",
+        default=True,
+        description="Toggles environment modifications",
+    )
+
     @staticmethod
     def update_description(cls):
         """Updates oneapi package descriptions with common text."""
@@ -114,11 +121,13 @@ class IntelOneApiPackage(Package):
 
            $ source {prefix}/{component}/{version}/env/vars.sh
         """
-        env.extend(
-            EnvironmentModifications.from_sourcing_file(
-                join_path(self.component_prefix, "env", "vars.sh")
+        # Only if environment modifications are desired (default is +envmods)
+        if "+envmods" in self.spec:
+            env.extend(
+                EnvironmentModifications.from_sourcing_file(
+                    join_path(self.component_prefix, "env", "vars.sh")
+                )
             )
-        )
 
 
 class IntelOneApiLibraryPackage(IntelOneApiPackage):
diff --git a/var/spack/repos/builtin/packages/intel-oneapi-mkl/package.py b/var/spack/repos/builtin/packages/intel-oneapi-mkl/package.py
index 41b8f12b12..62befb387d 100644
--- a/var/spack/repos/builtin/packages/intel-oneapi-mkl/package.py
+++ b/var/spack/repos/builtin/packages/intel-oneapi-mkl/package.py
@@ -131,8 +131,10 @@ class IntelOneapiMkl(IntelOneApiLibraryPackage):
             env.append_path("__INTEL_POST_FFLAGS", flag, separator=" ")
 
     def setup_dependent_build_environment(self, env, dependent_spec):
-        env.set("MKLROOT", self.component_prefix)
-        env.append_path("PKG_CONFIG_PATH", self.component_prefix.lib.pkgconfig)
+        # Only if environment modifications are desired (default is +envmods)
+        if "+envmods" in self.spec:
+            env.set("MKLROOT", self.component_prefix)
+            env.append_path("PKG_CONFIG_PATH", self.component_prefix.lib.pkgconfig)
 
     def _find_mkl_libs(self, shared):
         libs = []