Avoid the use of SSE instructions (R)SQRTSS for sqrtf and 1/sqrtf.

When using the -ffast-math option, GCC uses SSE instructions SQRTSS for
sqrtf and RSQRTSS for 1/sqrtf. This results in a loss of precision
according to the GCC documentation: "the precision of the sequence can
be decreased by up to 2 ulp (i.e. the inverse of 1.0 equals
0.99999994)".
This loss of precision affects some games.
Fixes the broken AI in Soldiers of Fortune.

shell/linux/Makefile

@@ -90,7 +90,7 @@ ifneq (,$(findstring x86,$(platform)))
     MFLAGS += -m32
     ASFLAGS += --32
     LDFLAGS += -m32
-    CFLAGS += -m32 -D TARGET_LINUX_x86 -D TARGET_NO_AREC -fsingle-precision-constant
+    CFLAGS += -m32 -D TARGET_LINUX_x86 -D TARGET_NO_AREC -fsingle-precision-constant -fno-builtin-sqrtf
     CXXFLAGS += -fno-exceptions
 
     ifneq (,$(findstring sse4_1,$(platform)))
@@ -102,7 +102,7 @@ else ifneq (,$(findstring x64,$(platform)))
     X64_REC := 1
     NOT_ARM := 1
     USE_X11 := 1
-    CFLAGS += -D TARGET_LINUX_x64 -D TARGET_NO_AREC -fsingle-precision-constant
+    CFLAGS += -D TARGET_LINUX_x64 -D TARGET_NO_AREC -fsingle-precision-constant -fno-builtin-sqrtf
     CXXFLAGS += -fexceptions
 
     ifneq (,$(findstring sse4_1,$(platform)))