treewide: handle postPhases __structuredAttrs-agnostically

Always specify the postPhases attribute as a list instead of a string.

Append elements to the postPhases Bash variable using appendToVar
instead of string or Bash array concatenation.

pkgs/build-support/release/binary-tarball.nix

@@ -24,7 +24,7 @@ stdenv.mkDerivation (
 
     prefix = "/usr/local";
 
-    postPhases = "finalPhase";
+    postPhases = [ "finalPhase" ];
   }
 
   // args //

pkgs/build-support/release/source-tarball.nix

@@ -32,7 +32,7 @@ stdenv.mkDerivation (
     showBuildStats = true;
 
     preConfigurePhases = [ "autoconfPhase" ];
-    postPhases = "finalPhase";
+    postPhases = [ "finalPhase" ];
 
     # Autoconfiscate the sources.
     autoconfPhase = ''

pkgs/build-support/setup-hooks/enable-coverage-instrumentation.sh

@@ -1,4 +1,4 @@
-postPhases+=" cleanupBuildDir"
+appendToVar postPhases cleanupBuildDir
 
 # Force GCC to build with coverage instrumentation.  Also disable
 # optimisation, since it may confuse things.

pkgs/build-support/setup-hooks/make-coverage-analysis-report.sh

@@ -1,4 +1,4 @@
-postPhases+=" coverageReportPhase"
+appendToVar postPhases coverageReportPhase
 
 coverageReportPhase() {
     lcov --directory . --capture --output-file app.info

pkgs/build-support/setup-hooks/move-build-tree.sh

@@ -5,7 +5,7 @@ moveBuildDir() {
     cd $out/.build
 }
 
-postPhases+=" removeBuildDir"
+appendToVar postPhases removeBuildDir
 
 removeBuildDir() {
     rm -rf $out/.build

pkgs/development/interpreters/python/hooks/python-recompile-bytecode-hook.sh

@@ -20,5 +20,5 @@ pythonRecompileBytecodePhase () {
 }
 
 if [ -z "${dontUsePythonRecompileBytecode-}" ]; then
-    postPhases+=" pythonRecompileBytecodePhase"
+    appendToVar postPhases pythonRecompileBytecodePhase
 fi

pkgs/development/libraries/qt-5/hooks/qtbase-setup-hook.sh

@@ -97,7 +97,7 @@ postPatchMkspecs() {
     fi
 }
 if [ -z "${dontPatchMkspecs-}" ]; then
-    postPhases="${postPhases-}${postPhases:+ }postPatchMkspecs"
+    appendToVar postPhases postPatchMkspecs
 fi
 
 qtPreHook() {

pkgs/development/libraries/qt-6/hooks/qtbase-setup-hook.sh

@@ -71,7 +71,7 @@ else # Only set up Qt once.
         fi
     }
     if [ -z "${dontPatchMkspecs-}" ]; then
-        postPhases="${postPhases-}${postPhases:+ }postPatchMkspecs"
+        appendToVar postPhases postPatchMkspecs
     fi
 
     qtPreHook() {