dev-lang/ghc: fix build with autoconf 2.71

Closes: https://bugs.gentoo.org/829162
Signed-off-by: Sam James <[email protected]>

dev-lang/ghc/files/ghc-8.8.4-autoconf-2.71.patch

@@ -0,0 +1,22 @@
+https://bugs.gentoo.org/829162
+https://gitlab.haskell.org/ghc/ghc/-/issues/19655
+https://gitlab.haskell.org/ghc/ghc/-/commit/ad2ef3a13f1eb000eab8e3d64592373b91a52806
+
+From: Moritz Angermann <[email protected]>
+Date: Wed, 17 Feb 2021 21:13:07 +0800
+Subject: [PATCH] [configure] Fix _AC_PROG_CC_99
+
+_AC_PROG_CC_99 isn't available anymore in recent autoconf versions.
+This broke on aarch64-darwin.
+--- a/aclocal.m4
++++ b/aclocal.m4
+@@ -659,7 +659,7 @@ AC_DEFUN([FP_SET_CFLAGS_C99],
+     CPPFLAGS="$$3"
+     unset ac_cv_prog_cc_c99
+     dnl perform detection
+-    _AC_PROG_CC_C99
++    AC_PROG_CC_C99
+     fp_cc_c99="$ac_cv_prog_cc_c99"
+     case "x$ac_cv_prog_cc_c99" in
+       x)   ;; # noop
+GitLab

dev-lang/ghc/ghc-8.8.4-r1.ebuild

@@ -510,6 +510,7 @@ src_prepare() {
 		eapply "${FILESDIR}"/${PN}-7.8.3-prim-lm.patch
 		eapply "${FILESDIR}"/${PN}-8.0.2-no-relax-everywhere.patch
 		eapply "${FILESDIR}"/${PN}-8.4.2-allow-cross-bootstrap.patch
+		eapply "${FILESDIR}"/${P}-autoconf-2.71.patch
 		# fixed in 8.8.4. See https://gitlab.haskell.org/ghc/ghc/-/blob/ghc-8.8.4-release/configure.ac#L1273
 		# eapply "${FILESDIR}"/${PN}-8.6.5-numa.patch
 		# rumors say this is fixed properly in 8.8.3. Let's check!