remove perl from path on appveyor

(cherry picked from commit 28cf580)

[av skip]

appveyor.yml

@@ -42,6 +42,9 @@ build_script:
 # Remove C:\MinGW\bin from the path, the version of MinGW installed on
 # AppVeyor is not compatible with the cross-compiled Julia Windows binaries
   - set PATH=%PATH:C:\MinGW\bin;=%
+# Remove C:\Perl\bin from the path, otherwise it breaks shasum with an error
+# Unable to find Digest::SHA or Digest::SHA::PurePerl
+  - set PATH=%PATH:C:\Perl\bin;=%
 #  - '"%VS120COMNTOOLS%\..\..\VC\vcvarsall.bat" x86_amd64'
 # Since the AppVeyor VMs have Git installed, they have MSYS1
   - sh --login /c/projects/julia/contrib/windows/msys_build.sh