Trac #29541: spkg-configure.m4 for giac

This ticket adds an spkg-configure.m4 for giac, in order to use it from
a system package if possible.

https://repology.org/project/giac/versions

See also:
 - #30537 Upgrade giac to 1.6.0-7

URL: https://trac.sagemath.org/29541
Reported by: gh-thierry-FreeBSD
Ticket author(s): Thierry Thomas, Matthias Koeppe
Reviewer(s): Isuru Fernando

build/pkgs/giac/distros/arch.txt

@@ -1 +1 @@
-libgiac
+libgiac giac

build/pkgs/giac/distros/conda.txt

@@ -0,0 +1 @@
+giac

build/pkgs/giac/distros/debian.txt

@@ -0,0 +1,2 @@
+libgiac-dev
+xcas

build/pkgs/giac/distros/fedora.txt

@@ -0,0 +1,2 @@
+giac
+giac-devel

build/pkgs/giac/distros/opensuse.txt

@@ -0,0 +1 @@
+giac

build/pkgs/giac/spkg-configure.m4

@@ -0,0 +1,26 @@
+SAGE_SPKG_CONFIGURE([giac], [
+    SAGE_SPKG_DEPCHECK([pari], [
+       dnl giac does not seem to reveal its patchlevel
+       m4_pushdef([GIAC_MIN_VERSION], [1.5.0])
+       m4_pushdef([GIAC_MAX_VERSION], [1.5.999])
+       AC_CACHE_CHECK([for giac >= ]GIAC_MIN_VERSION[, <= ]GIAC_MAX_VERSION, [ac_cv_path_GIAC], [
+         AC_PATH_PROGS_FEATURE_CHECK([GIAC], [giac], [
+            giac_version=$($ac_path_GIAC --version 2> /dev/null | tail -1)
+            AS_IF([test -n "$giac_version"], [
+                AX_COMPARE_VERSION([$giac_version], [ge], GIAC_MIN_VERSION, [
+                    AX_COMPARE_VERSION([$giac_version], [le], GIAC_MAX_VERSION, [
+                        ac_cv_path_GIAC="$ac_path_GIAC"
+                    ])
+                ])
+            ])
+         ])
+       ])
+       AS_IF([test -z "$ac_cv_path_GIAC"],
+             [sage_spkg_install_giac=yes])
+       AC_CHECK_HEADER([giac/giac.h], [
+        AC_SEARCH_LIBS([ConvertUTF16toUTF8], [giac], [
+        ], [sage_spkg_install_giac=yes])
+       ], [sage_spkg_install_giac=yes])
+       m4_popdef([GIAC_MIN_VERSION])
+    ])
+])