start, make built artifacts more reproducible but specifying -ffile-prefix-map

Author: ParkMyCar

toolchain/cc_toolchain_config.bzl

@@ -113,11 +113,12 @@ def cc_toolchain_config(
     unfiltered_compile_flags = [
         # Do not resolve our symlinked resource prefixes to real paths.
         "-no-canonical-prefixes",
-        # Reproducibility
+        # Reproducibility.
         "-Wno-builtin-macro-redefined",
         "-D__DATE__=\"redacted\"",
         "-D__TIMESTAMP__=\"redacted\"",
         "-D__TIME__=\"redacted\"",
+        "-ffile-prefix-map=${{pwd}}=__bazel_toolchain_llvm_repo__",
     ]
 
     is_xcompile = not (exec_os == target_os and exec_arch == target_arch)
@@ -150,6 +151,8 @@ def cc_toolchain_config(
     link_flags = [
         "--target=" + target_system_name,
         "-no-canonical-prefixes",
+        # Reproducibility.
+        "-ffile-prefix-map=${{pwd}}=__bazel_toolchain_llvm_repo__",
     ]
 
     stdlib = compiler_configuration["stdlib"]

toolchain/cc_wrapper.sh.tpl

@@ -53,6 +53,9 @@ function sanitize_option() {
     # shellcheck disable=SC2206
     parts=(${opt/=/ }) # Split flag name and value into array.
     printf "%s" "${parts[0]}=${execroot_path}${parts[1]}"
+  elif [[ ${opt} == *'${{pwd}}'* ]]; then
+    # Replace the literal string '${{pwd}}' with the execroot.
+    printf "%s" "${opt//'${{pwd}}'/${execroot_abs_path%/}}"
   else
     printf "%s" "${opt}"
   fi

toolchain/osx_cc_wrapper.sh.tpl

@@ -79,6 +79,9 @@ function sanitize_option() {
     # shellcheck disable=SC2206
     parts=(${opt/=/ }) # Split flag name and value into array.
     printf "%s" "${parts[0]}=${execroot_path}${parts[1]}"
+  elif [[ ${opt} == *'${{pwd}}'* ]]; then
+    # Replace the literal string '${{pwd}}' with the execroot.
+    printf "%s" "${opt//'${{pwd}}'/${execroot_abs_path%/}}"
   else
     printf "%s" "${opt}"
   fi
@@ -128,6 +131,8 @@ if [[ ":${PATH}:" != *":/usr/bin:"* ]]; then
   PATH="${PATH}:/usr/bin"
 fi
 
+echo "${cmd[@]}"
+
 # Call the C++ compiler.
 "${cmd[@]}"