Revert "fix: disable iwyu installation (for now)"

This reverts commit 21e9fe5.

Author: wdconinc

spack-environment/ci/spack.yaml

@@ -27,7 +27,7 @@ spack:
   - imagemagick
   - irt
   - irt2
-  #- iwyu  # FIXME disabled for now since it does not pick the external llvm
+  - iwyu
   - jana2
   - nopayloadclient
   - npsim -geocad

spack-environment/ci_without_acts/spack.yaml

@@ -26,7 +26,7 @@ spack:
   - imagemagick
   - irt
   - irt2
-  #- iwyu  # FIXME disabled for now since it does not pick the external llvm
+  - iwyu
   - jana2
   - nopayloadclient
   - npsim -geocad

spack-environment/cvmfs/spack.yaml

@@ -28,7 +28,7 @@ spack:
   - imagemagick
   - irt
   - irt2
-  #- iwyu  # FIXME disabled for now since it does not pick the external llvm
+  - iwyu
   - jana2
   - nopayloadclient
   - npsim -geocad

spack-environment/xl/spack.yaml

@@ -47,7 +47,7 @@ spack:
   - imagemagick
   - irt
   - irt2
-  #- iwyu  # FIXME disable for now since it does not pick the external llvm
+  - iwyu
   - jana2
   - k4actstracking
   - k4fwcore