Check for gperf at configure time

Edited Arne Babenhauserheide's patch
https://debbugs.gnu.org/cgi/bugreport.cgi?bug=51129;att=0;filename=0001-autoconf-Check-for-gperf-if-running-from-git.patch;msg=5.

Fixes https://debbugs.gnu.org/cgi/bugreport.cgi?bug=51129.

configure.ac

@@ -123,6 +123,14 @@ else
   fi
 fi
 
+# Gnulib uses gperf when building from git
+if ! test -f ".tarball-version"; then
+  AC_CHECK_TOOL([GPERF], [gperf], [no])
+  if test x"$GPERF" = x"no"; then
+    AC_MSG_ERROR([Building from git requires gperf. Please install it.])
+  fi
+fi
+
 gl_EARLY
 AC_PROG_CPP
 AC_PROG_SED
@@ -233,19 +241,19 @@ dnl  investigation of problems with "64" system and library calls on
 dnl  Darwin (MacOS X).  The libguile code (_scm.h) assumes that if a
 dnl  system has stat64, it will have all the other 64 APIs too; but on
 dnl  Darwin, stat64 is there but other APIs are missing.
-dnl 
+dnl
 dnl  It also appears, from the Darwin docs, that most system call APIs
 dnl  there (i.e. the traditional ones _without_ "64" in their names) have
 dnl  been 64-bit-capable for a long time now, so it isn't necessary to
 dnl  use "64" versions anyway.  For example, Darwin's off_t is 64-bit.
-dnl 
+dnl
 dnl  A similar problem has been reported for HP-UX:
 dnl  http://www.nabble.com/Building-guile-1.8.2-on-hpux-td13106681.html
-dnl 
+dnl
 dnl  Therefore, and also because a Guile without LARGEFILE64 support is
 dnl  better than no Guile at all, we provide this option to suppress
 dnl  trying to use "64" calls.
-dnl 
+dnl
 dnl  It may be that for some 64-bit function on Darwin/HP-UX we do need
 dnl  to use a "64" call, and hence that by using --without-64-calls we're
 dnl  missing out on that.  If so, someone can work on that in the future.
@@ -623,7 +631,7 @@ volatile complex double z = - _Complex_I;
 int
 main (void)
 {
-  z = csqrt (z);	
+  z = csqrt (z);
   if (creal (z) > 0.0)
     return 0;  /* good */
   else
@@ -742,9 +750,9 @@ AC_CHECK_SIZEOF(size_t)
 AC_CHECK_SIZEOF(ssize_t)
 ffi_size_type=uint$(($ac_cv_sizeof_size_t*8))
 ffi_ssize_type=sint$(($ac_cv_sizeof_ssize_t*8))
-AC_DEFINE_UNQUOTED([ffi_type_size_t], ffi_type_${ffi_size_type}, 
+AC_DEFINE_UNQUOTED([ffi_type_size_t], ffi_type_${ffi_size_type},
 		   [ffi type for size_t])
-AC_DEFINE_UNQUOTED([ffi_type_ssize_t], ffi_type_${ffi_ssize_type}, 
+AC_DEFINE_UNQUOTED([ffi_type_ssize_t], ffi_type_${ffi_ssize_type},
 		   [ffi type for ssize_t])
 
 dnl i18n tests
@@ -1115,7 +1123,7 @@ LIBS="$save_LIBS"
 
 AC_CHECK_SIZEOF(float)
 if test "$ac_cv_sizeof_float" -le "$ac_cv_sizeof_long"; then
-    AC_DEFINE([SCM_SINGLES], 1, 
+    AC_DEFINE([SCM_SINGLES], 1,
               [Define this if floats are the same size as longs.])
 fi
 
@@ -1246,7 +1254,7 @@ case "$with_threads" in
 
     # On Solaris, sched_yield lives in -lrt.
     AC_SEARCH_LIBS(sched_yield, rt)
-    
+
   ;;
 esac
 
@@ -1322,7 +1330,7 @@ GUILE_THREAD_LOCAL_STORAGE
 fi # with_threads=pthreads
 
 
-## Cross building	
+## Cross building
 if test "$cross_compiling" = "yes"; then
   AC_MSG_CHECKING(cc for build)
   ## /usr/bin/cc still uses wrong assembler
@@ -1330,8 +1338,8 @@ if test "$cross_compiling" = "yes"; then
   CC_FOR_BUILD="${CC_FOR_BUILD-PATH=/usr/bin:$PATH cc}"
 else
   CC_FOR_BUILD="${CC_FOR_BUILD-$CC}"
-fi   
+fi
-     
+
 ## AC_MSG_CHECKING("if we are cross compiling")
 ## AC_MSG_RESULT($cross_compiling)
 if test "$cross_compiling" = "yes"; then
@@ -1344,14 +1352,14 @@ CCLD_FOR_BUILD="$CC_FOR_BUILD"
 AC_SUBST(cross_compiling)
 AC_ARG_VAR(CC_FOR_BUILD,[build system C compiler])
 AC_SUBST(CCLD_FOR_BUILD)
-	
+
 ## libtool erroneously calls CC_FOR_BUILD HOST_CC;
 ## --HOST is the platform that PACKAGE is compiled for.
 HOST_CC="$CC_FOR_BUILD"
 AC_SUBST(HOST_CC)
 
 GUILE_CHECK_GUILE_FOR_BUILD
-  			
+
 ## If we're using GCC, add flags to reduce strictness of undefined
 ## behavior, and ask for aggressive warnings.
 GCC_CFLAGS=""