treewide: *Phase(s)? variables are optional

If these aren't defined, the stdenv defaults are used in the `*Phase`
case, or no extra phases are done, in the `*Phases` case.

pkgs/development/interpreters/python/hooks/flit-build-hook.sh

@@ -9,7 +9,7 @@ flitBuildPhase () {
     echo "Finished executing flitBuildPhase"
 }
 
-if [ -z "${dontUseFlitBuild-}" ] && [ -z "$buildPhase" ]; then
+if [ -z "${dontUseFlitBuild-}" ] && [ -z "${buildPhase-}" ]; then
     echo "Using flitBuildPhase"
     buildPhase=flitBuildPhase
 fi

pkgs/development/interpreters/python/hooks/pip-build-hook.sh

@@ -31,7 +31,7 @@ pipShellHook() {
     echo "Finished executing pipShellHook"
 }
 
-if [ -z "${dontUsePipBuild-}" ] && [ -z "$buildPhase" ]; then
+if [ -z "${dontUsePipBuild-}" ] && [ -z "${buildPhase-}" ]; then
     echo "Using pipBuildPhase"
     buildPhase=pipBuildPhase
 fi

pkgs/development/interpreters/python/hooks/pip-install-hook.sh

@@ -18,7 +18,7 @@ pipInstallPhase() {
     echo "Finished executing pipInstallPhase"
 }
 
-if [ -z "${dontUsePipInstall-}" ] && [ -z "$installPhase" ]; then
+if [ -z "${dontUsePipInstall-}" ] && [ -z "${installPhase-}" ]; then
     echo "Using pipInstallPhase"
     installPhase=pipInstallPhase
 fi

pkgs/development/interpreters/python/hooks/pytest-check-hook.sh

@@ -43,7 +43,7 @@ function pytestCheckPhase() {
     echo "Finished executing pytestCheckPhase"
 }
 
-if [ -z "${dontUsePytestCheck-}" ] && [ -z "$installCheckPhase" ]; then
+if [ -z "${dontUsePytestCheck-}" ] && [ -z "${installCheckPhase-}" ]; then
     echo "Using pytestCheckPhase"
     preDistPhases+=" pytestCheckPhase"
 fi

pkgs/development/interpreters/python/hooks/setuptools-build-hook.sh

@@ -36,12 +36,12 @@ setuptoolsShellHook() {
     echo "Finished executing setuptoolsShellHook"
 }
 
-if [ -z "${dontUseSetuptoolsBuild-}" ] && [ -z "$buildPhase" ]; then
+if [ -z "${dontUseSetuptoolsBuild-}" ] && [ -z "${buildPhase-}" ]; then
     echo "Using setuptoolsBuildPhase"
     buildPhase=setuptoolsBuildPhase
 fi
 
-if [ -z "${dontUseSetuptoolsShellHook-}" ] && [ -z "$shellHook" ]; then
+if [ -z "${dontUseSetuptoolsShellHook-}" ] && [ -z "${shellHook-}" ]; then
     echo "Using setuptoolsShellHook"
     shellHook=setuptoolsShellHook
 fi

pkgs/development/interpreters/python/hooks/setuptools-check-hook.sh

@@ -12,7 +12,7 @@ setuptoolsCheckPhase() {
     echo "Finished executing setuptoolsCheckPhase"
 }
 
-if [ -z "${dontUseSetuptoolsCheck-}" ] && [ -z "$installCheckPhase" ]; then
+if [ -z "${dontUseSetuptoolsCheck-}" ] && [ -z "${installCheckPhase-}" ]; then
     echo "Using setuptoolsCheckPhase"
     preDistPhases+=" setuptoolsCheckPhase"
 fi

pkgs/development/interpreters/python/hooks/wheel-unpack-hook.sh

@@ -12,7 +12,7 @@ wheelUnpackPhase(){
     echo "Finished executing wheelUnpackPhase"
 }
 
-if [ -z "${dontUseWheelUnpack-}" ] && [ -z "$unpackPhase" ]; then
+if [ -z "${dontUseWheelUnpack-}" ] && [ -z "${unpackPhase-}" ]; then
     echo "Using wheelUnpackPhase"
     unpackPhase=wheelUnpackPhase
 fi