allow building sysimage with custom PyCall

src/julia/compile.jl

@@ -1,4 +1,4 @@
-compiler_env, script, output, base_sysimage = ARGS
+compiler_env, pycall_env, script, output, base_sysimage = ARGS
 
 if VERSION < v"0.7-"
     error("Unsupported Julia version $VERSION")
@@ -11,40 +11,42 @@ Pkg.activate(compiler_env)
 @info "Loading PackageCompiler..."
 using PackageCompiler
 
-@info "Installing PyCall..."
-Pkg.activate(".")
-Pkg.add([
-    Pkg.PackageSpec(
-        name = "PyCall",
-        uuid = "438e738f-606a-5dbb-bf0a-cddfbfd45ab0",
-    ),
-])
+Pkg.activate(pycall_env)
+if pycall_env == "."
+    @info "Installing PyCall..."
+    Pkg.add([
+        Pkg.PackageSpec(
+            name = "PyCall",
+            uuid = "438e738f-606a-5dbb-bf0a-cddfbfd45ab0",
+        ),
+    ])
+end
 
 if VERSION >= v"1.5-"
     mktempdir() do dir
         tmpimg = joinpath(dir, basename(output))
-        @info "Compiling a temporary system image without `PyCall`..."
+        @info "Compiling a temporary system image without PyCall..."
         create_sysimage(
             Symbol[];
             sysimage_path = tmpimg,
-            project = ".",
+            project = pycall_env,
             base_sysimage = isempty(base_sysimage) ? nothing : base_sysimage,
         )
-        @info "Compiling system image..."
+        @info "Compiling system image with PyCall from $pycall_env..."
         create_sysimage(
             [:PyCall];
             sysimage_path = output,
-            project = ".",
+            project = pycall_env,
             precompile_execution_file = script,
             base_sysimage = tmpimg,
         )
     end
 else
-    @info "Compiling system image..."
+    @info "Compiling system image with PyCall from $pycall_env..."
     create_sysimage(
         [:PyCall],
         sysimage_path = output,
-        project = ".",
+        project = pycall_env,
         precompile_execution_file = script,
         base_sysimage = isempty(base_sysimage) ? nothing : base_sysimage,
     )

src/julia/sysimage.py

@@ -79,6 +79,7 @@ def build_sysimage(
     script=script_path("precompile.jl"),
     debug=False,
     compiler_env="",
+    pycall_env="",
     base_sysimage=None,
 ):
     if debug:
@@ -90,15 +91,24 @@ def build_sysimage(
     julia_py = julia_py_executable()
 
     with temporarydirectory(prefix="tmp.pyjulia.sysimage.") as path:
-        if not compiler_env:
+
+        if compiler_env:
+            compiler_env = os.path.abspath(compiler_env)
+        else:
             compiler_env = os.path.join(path, "compiler_env")
             # Not using julia-py to install PackageCompiler to reduce
             # method re-definition warnings:
             check_call(install_packagecompiler_cmd(julia, compiler_env), cwd=path)
 
+        if pycall_env:
+            pycall_env = os.path.abspath(pycall_env)
+        else:
+            pycall_env = "."
+
         # Arguments to ./compile.jl script:
         compile_args = [
             compiler_env,
+            pycall_env,
             # script -- ./precompile.jl by default
             os.path.realpath(script),
             # output -- path to sys.o file
@@ -131,10 +141,18 @@ def main(args=None):
         "--compiler-env",
         default="",
         help="""
-        Path to a Julia project with PackageCompiler to be used for
-        system image compilation.  Create a temporary environment with
-        appropriate PackageCompiler by default or when an empty string
-        is given.
+        Path to a Julia project with PackageCompiler to be used for system image
+        compilation. If none is provided, will create a temporary environment
+        with the latest version of PackageCompiler.
+        """,
+    )
+    parser.add_argument(
+        "--pycall-env",
+        default="",
+        help="""
+        Path to a Julia project with PyCall to be used for system image
+        compilation. If none is provided, will create a temporary environment
+        with the latest version of PyCall.
         """,
     )
     parser.add_argument(