This is only relevant on case-insensitive OS's like OS X.
If cvsclean in build/build.mk is run - because of a version of autoconf more recent than 2.13, for instance - it ends
up deleting the pear/PEAR directory, because pear/.cvsignore
contains "pear". The easiest way to fix the immediate problem would be to add a 'grep -v pear', but this is an attempt to solve the general problem of matching case:

Index: build.mk
===================================================================
RCS file: /repository/php4/build/build.mk,v
retrieving revision 1.18
diff -u -r1.18 build.mk
--- build.mk    21 Oct 2002 15:11:19 -0000      1.18
+++ build.mk    20 Apr 2003 14:48:52 -0000
@@ -67,7 +67,7 @@
 
 cvsclean:
        @for i in `find . -name .cvsignore`; do \
-               (cd `dirname $$i` 2>/dev/null && rm -rf `cat .cvsignore | grep -v config.nice` *.o *.a .libs || true); \
+               (cd `dirname $$i` 2>/dev/null && cat .cvsignore | grep -v config.nice | xargs -n1 find . -maxdepth 1 -name | xargs -n1 rm -rfv && rm -rfv *.o *.a .libs || true); \
        done
 
 .PHONY: $(ALWAYS) snapshot cvsclean