expat: Revert to bz2 distfile to avoid dep cycle

textproc/expat/Portfile

@@ -8,9 +8,9 @@ PortGroup muniversal 1.0
 name expat
 version 2.4.1
 revision 0
-checksums rmd160 33e0942f221daf3c97f4e8056cdf722b80e338d5 \
- sha256 8541697089dec1e28a2ec834adc135d18f47e1db8c829af469eb46bbab87cefc \
- size 443612
+checksums rmd160 1b86f6709b9e233aa5cc98c4388d2e2a2942667c \
+ sha256 2f9b6a580b94577b150a7d5617ad4643a4301a6616ff459307df3e225bcfbf40 \
+ size 551055
 
 categories textproc devel
 platforms darwin freebsd
@@ -26,7 +26,10 @@ long_description Expat is an XML parser library written in C. It is a \
 
 homepage https://www.libexpat.org/
 master_sites sourceforge:project/${name}/${name}/${version}
-use_lzip yes
+# Don't use a compression format that necessitates a dependency on another
+# port since that causes a dependency cycle on older OS versions since
+# e.g. clang-3.4 depends on python27-bootstrap which depends on expat.
+use_bzip2 yes
 
 if {${os.platform} eq "darwin" && ${os.major} < 11} {
  # Having the stdlib set to libc++ on 10.6 causes a dependency on a