Set JULIA_PROJECT when running the subprocess in ensurecompiled()

Author: DilumAluthge

src/PackageCompiler.jl

@@ -299,8 +299,9 @@ function ensurecompiled(project, packages, sysimage)
     # TODO: Only precompile `packages` (should be available in Pkg 1.8)
     cmd = `$(get_julia_cmd()) --sysimage=$sysimage -e 'using Pkg; Pkg.precompile()'`
     splitter = Sys.iswindows() ? ';' : ':'
-    @debug "ensurecompiled: running $cmd" JULIA_LOAD_PATH = "$project$(splitter)@stdlib"
-    cmd = addenv(cmd, "JULIA_LOAD_PATH" => "$project$(splitter)@stdlib")
+    JULIA_LOAD_PATH = "$project$(splitter)@stdlib"
+    @debug "ensurecompiled: running $cmd" JULIA_LOAD_PATH
+    cmd = setenv(cmd, "JULIA_LOAD_PATH" => JULIA_LOAD_PATH, "JULIA_PROJECT" => project)
     run(cmd)
     return
 end