Fix forward erasure (rust-lang#653)

Author: wsmoses

.github/workflows/enzyme-julia.yml

@@ -39,10 +39,17 @@ jobs:
       with:
         version: ${{ matrix.version }}
         arch: ${{ matrix.arch }}
+
     - name: Build libEnzyme
+      if: ${{ matrix.os != 'macOS-latest'}}
       run: |
         julia --project=jl/deps -e 'using Pkg; Pkg.instantiate()'
         julia --project=jl/deps jl/deps/build_local.jl ./enzyme
+    - name: Build libEnzyme MacOS
+      if: ${{ matrix.os == 'macOS-latest'}}
+      run: |
+        julia --project=jl/deps -e 'using Pkg; Pkg.instantiate()'
+        SDKROOT=`xcrun --show-sdk-path` julia --project=jl/deps jl/deps/build_local.jl ./enzyme
     - uses: julia-actions/julia-buildpkg@v1
       with:
         project: jl

enzyme/Enzyme/AdjointGenerator.h

@@ -8275,8 +8275,7 @@ class AdjointGenerator
           assert(normalReturn->getType() == newCall->getType());
           gutils->replaceAWithB(newCall, normalReturn);
           gutils->erase(newCall);
-        } else
-          eraseIfUnused(*orig);
+        }
         return;
       }
     }