Compilation error

[Ekaitz Zarraga]

Hi,

I get the following error message when compiling the latest commit of recutils.

The 1.8 version compiles with no issues. I didn't test (yet) any commits in 
between.


```
 ./configure
checking for a BSD-compatible install... 
/gnu/store/2g0ky5gb0fsnw2xn5vyy6ydwl8mfx8mh-profile/bin/install -c
checking whether build environment is sane... yes
checking for a race-free mkdir -p... 
/gnu/store/2g0ky5gb0fsnw2xn5vyy6ydwl8mfx8mh-profile/bin/mkdir -p
checking for gawk... gawk
checking whether make sets $(MAKE)... yes
checking whether make supports nested variables... yes
checking build system type... x86_64-pc-linux-gnu
checking host system type... x86_64-pc-linux-gnu
configure: autobuild project... GNU recutils
configure: autobuild revision... 1.8.90
configure: autobuild hostname... tuxedo
configure: autobuild timestamp... 20210115T233619Z
checking for gcc... gcc
checking whether the C compiler works... yes
checking for C compiler default output file name... a.out
checking for suffix of executables...
checking whether we are cross compiling... no
checking for suffix of object files... o
checking whether the compiler supports GNU C... yes
checking whether gcc accepts -g... yes
checking for gcc option to enable C11 features... none needed
./configure: line 6102: syntax error near unexpected token 
`ac_cv_prog_cc_stdc=$ac_cv_prog_cc_c89'
./configure: line 6102: `                     
ac_cv_prog_cc_stdc=$ac_cv_prog_cc_c89'
```

All the best,
Ekaitz