imagemagick: --without-gcc-arch

ax_gcc_archflag has no Zen cpuid pattern and falls back to
-mtune=amdfam10, which under LLVM+LTO emits SSE4a extrq and SIGILLs on
Intel hosts. Disable the implicit --with-gcc-arch so host CPU features
do not bleed into the built binaries.

src/Package/Library/imagemagick.php

@@ -42,6 +42,9 @@ class imagemagick
             ->addConfigureArgs(
                 '--disable-openmp',
                 '--without-x',
+                // implicit --with-gcc-arch
+                // bleeds host cpu features into built binaries
+                '--without-gcc-arch',
             );
 
         // special: linux-static target needs `-static`