Prevent implicit conversion of float to double to avoid precision
error on i686.

  https://github.com/Maratyszcza/FP16/issues/20

Taken from Debian:

  https://salsa.debian.org/deeplearning-team/fp16/-/blob/master/debian/patches/ftbfs-i386.patch

Index: fp16/include/fp16/fp16.h
===================================================================
--- fp16.orig/include/fp16/fp16.h
+++ fp16/include/fp16/fp16.h
@@ -228,7 +228,8 @@ static inline uint16_t fp16_ieee_from_fp
 	const float scale_to_inf = fp32_from_bits(UINT32_C(0x77800000));
 	const float scale_to_zero = fp32_from_bits(UINT32_C(0x08800000));
 #endif
-	float base = (fabsf(f) * scale_to_inf) * scale_to_zero;
+	const volatile float base_inf = fabsf(f) * scale_to_inf;
+	float base = base_inf * scale_to_zero;
 
 	const uint32_t w = fp32_to_bits(f);
 	const uint32_t shl1_w = w + w;
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<tr><td><span title='2021-12-13 17:48:25 +0100'>2021-12-13</span></td><td><a href='/guix/commit/gnu/packages/slang.scm?id=8394619baceb118df92e355377fd543bb1aa501a'>gnu: Simplify package inputs.</a><span class='msg-avail'>...<span class='msg-tooltip'>This commit was obtained by running:

  ./pre-inst-env guix style

without any additional argument.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-11-26 00:01:54 -0500'>2021-11-26</span></td><td><a href='/guix/commit/gnu/packages/slang.scm?id=3672f515825132be74d9729ed5778daab33ae64e'>gnu: slang: Really fix the array tests on 32 bit architectures.</a><span class='msg-avail'>...<span class='msg-tooltip'>This is a follow up to efb0a04ee05f43e86b3c1fcda867a123d8ed021a.

* gnu/packages/slang.scm (slang)[phases]{reduce-array-test-size}: Further
reduce the array size.
</span></span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2021-11-25 17:08:11 -0500'>2021-11-25</span></td><td><a href='/guix/commit/gnu/packages/slang.scm?id=efb0a04ee05f43e86b3c1fcda867a123d8ed021a'>gnu: slang: Fix build on 32 bit systems.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/slang.scm (slang)[phases]{reduce-array-test-size}: New phase.
</span></span></td><td>Maxim Cournoyer</td></tr>