boot: Move boot_zlib build out of tarfs directory.

It is also used by packagefs. Another library is coming in the next commit.

src/system/boot/Jamfile

@@ -401,5 +401,6 @@ for platform in [ MultiBootSubDirSetup ] {
 }
 
 SubInclude HAIKU_TOP src system boot arch $(TARGET_KERNEL_ARCH_DIR) ;
+SubInclude HAIKU_TOP src system boot libs ;
 SubInclude HAIKU_TOP src system boot loader ;
 SubInclude HAIKU_TOP src system boot platform ;

src/system/boot/libs/Jamfile

@@ -0,0 +1,34 @@
+SubDir HAIKU_TOP src system boot libs ;
+
+local zlibSourceDirectory = [ BuildFeatureAttribute zlib : sources : path ] ;
+UseHeaders $(zlibSourceDirectory) ;
+UseHeaders $(zlibSourceDirectory) : true ;
+
+DEFINES += _BOOT_MODE ;
+
+local zlibSources =
+	adler32.c
+	crc32.c
+	inffast.c
+	inflate.c
+	inftrees.c
+	uncompr.c
+	zutil.c
+	;
+
+local platform ;
+for platform in [ MultiBootSubDirSetup ] {
+	on $(platform) {
+		# zlib
+		UsePrivateHeaders [ FDirName kernel boot platform $(TARGET_BOOT_PLATFORM) ] ;
+
+		LOCATE on [ FGristFiles $(zlibSources) ] = $(zlibSourceDirectory) ;
+
+		Depends [ FGristFiles $(zlibSources) ]
+			: [ BuildFeatureAttribute zlib : sources ] ;
+
+		BootStaticLibrary [ MultiBootGristFiles boot_zlib ] :
+			$(zlibSources)
+			;
+	}
+}

src/system/boot/loader/file_systems/tarfs/Jamfile

@@ -3,47 +3,21 @@ SubDir HAIKU_TOP src system boot loader file_systems tarfs ;
 UsePrivateHeaders [ FDirName kernel disk_device_manager ] ;
 UsePrivateHeaders kernel shared storage ;
 
-local zlibSourceDirectory = [ BuildFeatureAttribute zlib : sources : path ] ;
-UseHeaders $(zlibSourceDirectory) ;
-UseHeaders $(zlibSourceDirectory) : true ;
+UseBuildFeatureHeaders zlib ;
 
 local defines = [ FDefines _BOOT_MODE ] ;
 SubDirCcFlags $(defines) ;
 SubDirC++Flags -fno-rtti $(defines) ;
 
-
-local zlibSources =
-	adler32.c
-	crc32.c
-	inffast.c
-	inflate.c
-	inftrees.c
-	uncompr.c
-	zutil.c
-	;
-
 local platform ;
 for platform in [ MultiBootSubDirSetup ] {
 	on $(platform) {
 		UsePrivateHeaders [ FDirName kernel boot platform $(TARGET_BOOT_PLATFORM) ] ;
 
-		LOCATE on [ FGristFiles $(zlibSources) ] = $(zlibSourceDirectory) ;
-		Depends [ FGristFiles $(zlibSources) ]
-			: [ BuildFeatureAttribute zlib : sources ] ;
-
-		BootStaticLibrary [ MultiBootGristFiles boot_zlib ] :
-			$(zlibSources)
-			;
-
-
-		Includes [ FGristFiles tarfs.cpp ] : [ BuildFeatureAttribute zlib : sources ] ;
-			# Strictly speaking it should be "headers", but the sources contain the
-			# headers as well and we have already added the sources directory to the
-			# header search path for the subdirectory. Should building boot_zlib be
-			# moved to its own directory, this should better be changes as well.
-
 		BootStaticLibrary [ MultiBootGristFiles boot_tarfs ] :
 			tarfs.cpp
 			;
+
+		Includes [ FGristFiles tarfs.cpp ] : [ BuildFeatureAttribute zlib : headers ] ;
 	}
 }