firefox: 68esr: Provide symbolic link for python2.7 when firefox 68esr is built

This hack/workaround allows building the firefox 68esr on Centos/Fedora.
Detailed description of the problem:
#338

Firefox's bugzilla entry:
https://bugzilla.mozilla.org/show_bug.cgi?id=1651641

Signed-off-by: Lukasz Majewski <lukma@denx.de>

Author: Lukasz Majewski

meta-firefox/classes/mozilla.bbclass

@@ -3,7 +3,7 @@ DEPENDS += "gnu-config-native virtual/libintl libxt libxi zip-native gtk+"
 
 SRC_URI += "file://mozconfig"
 
-inherit pkgconfig
+inherit pkgconfig pythonnative
 
 EXTRA_OECONF = "--target=${TARGET_SYS} --host=${BUILD_SYS} \
                 --with-toolchain-prefix=${TARGET_SYS}- \
@@ -62,6 +62,15 @@ mozilla_do_configure() {
 }
 
 mozilla_do_compile() {
+
+	# This is a hack/workaround necessary for building firefox 68esr on
+	# Centos 7.6/Fedora
+	# It doesn't do any harm on other distros - like Ubuntu 18.04 or Debian 10
+	# Moreover, it mimics 'include pythonnative', which cannot be used as it
+	# causes errors during firefox 68esr configuration stage
+	ln -snf python-native/python2.7 ${STAGING_BINDIR_NATIVE}/python2.7
+	ln -snf python-native/python2.7 ${STAGING_BINDIR_NATIVE}/python
+
 	mozilla_run_mach build
 }
 

meta-firefox/conf/layer.conf

@@ -4,14 +4,6 @@ BBPATH .= ":${LAYERDIR}"
 # We have a recipes directory, add to BBFILES
 BBFILES += "${LAYERDIR}/recipes-*/*/*.bb ${LAYERDIR}/recipes-*/*/*.bbappend"
 
-# this is only temporary to allow building firefox on hosts without any python2
-# were it would fail like this:
-# ERROR: firefox-68.9.0esr-r0 do_configure: Execution of '/OE/build/oe-core/tmp-glibc/work/core2-64-oe-linux/firefox/68.9.0esr-r0/temp/run.do_configure.2697230' failed with exit code 127:
-# ./mach: 9: exec: python: not found
-# this should be removed when firefox is upgraded to 78 ESR or newer which contains:
-# https://bugzilla.mozilla.org/show_bug.cgi?id=1473498
-HOSTTOOLS += "python python2.7"
-
 SIGGEN_EXCLUDERECIPES_ABISAFE += " \
    firefox-addon-webconverger \
    firefox-l10n-ach \