[Buildroot] [PATCH 2/3] package/environment-setup: make script idempotent

[Konrad Schwarz]

One (slight) problem with this kind of environment setup files is when they
are executed repeatedly (e.g., because something else is not quite right
yet), they tend to extend the PATH variable with the same directory,
creating a very unwieldy search path and potentially slowing down
searches for executable files.

This fix adds a test such that PATH is extended only when necessary.

The code has also been simplified
(using standard POSIX shell features) and make the generated
script more readable, e.g., by splitting overly long lines.

Signed-off-by: Konrad Schwarz <konrad.schwarz at siemens.com>
---
 .../environment-setup/environment-setup.mk    | 60 +++++++++----------
 1 file changed, 30 insertions(+), 30 deletions(-)

diff --git a/package/environment-setup/environment-setup.mk b/package/environment-setup/environment-setup.mk
index fcad013f0d..5cb703e421 100644
--- a/package/environment-setup/environment-setup.mk
+++ b/package/environment-setup/environment-setup.mk
@@ -4,38 +4,38 @@
 #
 ################################################################################
 
-ENVIRONMENT_SETUP_FILE = $(HOST_DIR)/environment-setup
-
 define HOST_ENVIRONMENT_SETUP_INSTALL_CMDS
-	cp package/environment-setup/environment-setup $(ENVIRONMENT_SETUP_FILE)
-	for var in $(TARGET_CONFIGURE_OPTS); do \
-		printf "export \"$$var\"\n" >> $(ENVIRONMENT_SETUP_FILE); \
-	done
-	printf "export \"ARCH=$(KERNEL_ARCH)\"\n" >> $(ENVIRONMENT_SETUP_FILE)
-	printf "export \"CROSS_COMPILE=$(TARGET_CROSS)\"\n" >> $(ENVIRONMENT_SETUP_FILE)
-	printf "export \"CONFIGURE_FLAGS=--target=$(GNU_TARGET_NAME) \
-		--host=$(GNU_TARGET_NAME) \
-		--build=$(GNU_HOST_NAME) \
-		--prefix=/usr \
-		--exec-prefix=/usr \
-		--sysconfdir=/etc \
-		--localstatedir=/var \
-		--program-prefix=\"\n" >> $(ENVIRONMENT_SETUP_FILE)
-	printf "alias configure=\"./configure \$${CONFIGURE_FLAGS}\"\n" \
-		>> $(ENVIRONMENT_SETUP_FILE)
-	printf "alias cmake=\"cmake \
-		-DCMAKE_TOOLCHAIN_FILE=$(HOST_DIR)/share/buildroot/toolchainfile.cmake \
-		-DCMAKE_INSTALL_PREFIX=/usr\"\n" >> $(ENVIRONMENT_SETUP_FILE)
-	$(SED) 's%$(HOST_DIR)%\$$SDK_PATH%g' \
-		-e 's%$(HOST_DIR)/bin/%%g' \
-		-e '/^export "PATH=/c\' \
-		$(ENVIRONMENT_SETUP_FILE)
-	printf "export \"PATH=\$$SDK_PATH/bin:\$$SDK_PATH/sbin:\$$PATH\"\n" \
-		>> $(ENVIRONMENT_SETUP_FILE)
-
+	{ \
+	cat package/environment-setup/environment-setup &&\
+	printf 'export "%s"\n' $(TARGET_CONFIGURE_OPTS) &&\
+	printf %b\
+	'export "ARCH=$(KERNEL_ARCH)"\n'\
+	'export "CROSS_COMPILE=$(TARGET_CROSS)"\n'\
+	'export CONFIGURE_FLAGS=\\\n'\
+		'"--target=$(GNU_TARGET_NAME) "\\\n'\
+		'"--host=$(GNU_TARGET_NAME) "\\\n'\
+		'"--build=$(GNU_HOST_NAME) "\\\n'\
+		'"--prefix=/usr "\\\n'\
+		'"--exec-prefix=/usr "\\\n'\
+		'"--sysconfdir=/etc "\\\n'\
+		'"--localstatedir=/var "\\\n'\
+		'"--program-prefix= "\n'\
+	'alias configure="./configure \$$CONFIGURE_FLAGS"\n'\
+	'alias cmake="cmake"\\\n'\
+		'" -DCMAKE_TOOLCHAIN_FILE'\
+		'=$(HOST_DIR)/share/buildroot/toolchainfile.cmake"\\\n'\
+		'" -DCMAKE_INSTALL_PREFIX=/usr"\n'\
+	'if ! command -v $${CROSS_COMPILE}gcc > /dev/null\n'\
+	'then	export PATH="$$SDK_PATH/bin:$$SDK_PATH/sbin:$$PATH"\n'\
+	'fi\n'\
+	\
 	$(if $(BR2_LINUX_KERNEL),\
-		printf "export \"KERNELDIR=$(LINUX_BUILDDIR)\"\n" \
-			>> $(ENVIRONMENT_SETUP_FILE),)
+		'export "KERNELDIR=$(LINUX_BUILDDIR)"\n')\
+	; } |\
+	sed -e 's%$(HOST_DIR)%\$$SDK_PATH%g'\
+		-e 's%$(HOST_DIR)/bin/%%g'\
+		-e '/^export "PATH=/c\'\
+		>$(HOST_DIR)/environment-setup
 endef
 
 $(eval $(host-generic-package))
-- 
2.25.4