build: drop Python 3.9 support.

All on-tree users should already be targetting 3.10.

dev-python/build/build-1.2.2.recipe

@@ -4,7 +4,7 @@ It is a simple build tool and does not perform any dependency management."
 HOMEPAGE="https://pypi.org/project/build/"
 COPYRIGHT="2019 Filipe Laíns"
 LICENSE="MIT"
-REVISION="1"
+REVISION="2"
 SOURCE_URI="https://files.pythonhosted.org/packages/source/b/build/build-$portVersion.tar.gz"
 CHECKSUM_SHA256="119b2fb462adef986483438377a13b2f42064a2a3a4161f24a0cca698a07ac8c"
 
@@ -21,11 +21,10 @@ BUILD_REQUIRES="
 	haiku_devel
 	"
 
-PYTHON_VERSIONS=(3.9 3.10)
+PYTHON_VERSIONS=(3.10)
 defaultVersion=3.10
 
-for i in "${!PYTHON_VERSIONS[@]}"; do
-	pythonVersion=${PYTHON_VERSIONS[$i]}
+for pythonVersion in ${PYTHON_VERSIONS[@]}; do
 	pythonPackage=python${pythonVersion//.}
 
 	eval "PROVIDES_$pythonPackage=\"
@@ -61,8 +60,7 @@ done
 
 INSTALL()
 {
-	for i in "${!PYTHON_VERSIONS[@]}"; do
-		pythonVersion=${PYTHON_VERSIONS[$i]}
+	for pythonVersion in ${PYTHON_VERSIONS[@]}; do
 		pythonPackage=python${pythonVersion//.}
 
 		python=python$pythonVersion